Convert another 45 monster loops to monster_iterator.

A total of 53 have been converted; 39 left, of which some should
stay. Now at a net loss of lines of code for monster_iterator.

Occurrences of MAX_MONSTERS down to 65 from 116 in *.cc.

16 files changed, 388 insertions, 516 deletions

diff --git a/crawl-ref/source/abyss.cc b/crawl-ref/source/abyss.cc
index cf3f74267d..e5d64fff31 100644
--- a/crawl-ref/source/abyss.cc
+++ b/crawl-ref/source/abyss.cc
@@ -18,6 +18,7 @@
 #include "mapmark.h"
 #include "message.h"
 #include "misc.h"
+#include "mon-iter.h"
 #include "mon-util.h"
 #include "monplace.h"
 #include "mtransit.h"
@@ -442,16 +443,11 @@ void area_shift(void)
 
     _xom_check_nearness_setup();
 
-    for (unsigned int i = 0; i < MAX_MONSTERS; i++)
+    // Remove non-nearby monsters.
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters &m = menv[i];
-
-        if (!m.alive())
-            continue;
-
-        // Remove non-nearby monsters.
-        if (grid_distance(m.pos(), you.pos()) > 10)
-            _abyss_lose_monster(m);
+        if (grid_distance(mi->pos(), you.pos()) > 10)
+            _abyss_lose_monster(**mi);
     }
 
     for (rectangle_iterator ri(5); ri; ++ri)
@@ -546,12 +542,9 @@ void area_shift(void)
 
 void save_abyss_uniques()
 {
-    for (int i = 0; i < MAX_MONSTERS; ++i)
-    {
-        monsters &m = menv[i];
-        if (m.alive() && m.needs_transit())
-            m.set_transit( level_id(LEVEL_ABYSS) );
-    }
+    for (monster_iterator mi; mi; ++mi)
+         if (mi->needs_transit())
+            mi->set_transit(level_id(LEVEL_ABYSS));
 }
 
 void abyss_teleport( bool new_area )
@@ -602,9 +595,8 @@ void abyss_teleport( bool new_area )
     tile_init_flavour();
 #endif
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
-        if (menv[i].alive())
-            _abyss_lose_monster(menv[i]);
+    for (monster_iterator mi; mi; ++mi)
+        _abyss_lose_monster(**mi);
 
     // Orbs and fixed artefacts are marked as "lost in the abyss".
     for (int i = 0; i < MAX_ITEMS; ++i)
diff --git a/crawl-ref/source/acr.cc b/crawl-ref/source/acr.cc
index ff1a1ccd3b..70901ec1cb 100644
--- a/crawl-ref/source/acr.cc
+++ b/crawl-ref/source/acr.cc
@@ -89,6 +89,7 @@
 #include "misc.h"
 #include "mon-act.h"
 #include "mon-cast.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monstuff.h"
 #include "mon-util.h"
@@ -4025,9 +4026,8 @@ static void _move_player(coord_def move)
         mprf(MSGCH_DIAGNOSTICS, "Number of items present: %d", j);
 
         j = 0;
-        for (int i = 0; i < MAX_MONSTERS; ++i)
-            if (menv[i].type != -1)
-                ++j;
+        for (monster_iterator mi; mi; ++mi)
+            ++j;
 
         mprf(MSGCH_DIAGNOSTICS, "Number of monsters present: %d", j);
         mprf(MSGCH_DIAGNOSTICS, "Number of clouds present: %d", env.cloud_no);
diff --git a/crawl-ref/source/attitude-change.cc b/crawl-ref/source/attitude-change.cc
index 509525fb65..518d77cb9a 100644
--- a/crawl-ref/source/attitude-change.cc
+++ b/crawl-ref/source/attitude-change.cc
@@ -16,6 +16,7 @@
 #include "goditem.h"
 #include "message.h"
 #include "mon-behv.h"
+#include "mon-iter.h"
 #include "mon-util.h"
 #include "monster.h"
 #include "monstuff.h"
@@ -145,44 +146,42 @@ static bool _holy_beings_on_level_attitude_change()
 {
     bool success = false;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (monster->alive()
-            && monster->is_holy())
-        {
+        if (!mi->is_holy())
+            continue;
+
 #ifdef DEBUG_DIAGNOSTICS
-            mprf(MSGCH_DIAGNOSTICS, "Holy attitude changing: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
-                 static_cast<int>(you.your_level),
-                 static_cast<int>(you.where_are_you));
+        mprf(MSGCH_DIAGNOSTICS, "Holy attitude changing: %s on level %d, branch %d",
+             mi->name(DESC_PLAIN).c_str(),
+             static_cast<int>(you.your_level),
+             static_cast<int>(you.where_are_you));
 #endif
 
-            // If you worship a good god, you get another chance to make
-            // neutral and hostile holy beings good neutral.
-            if (is_good_god(you.religion) && !monster->wont_attack())
-            {
-                if (testbits(monster->flags, MF_ATT_CHANGE_ATTEMPT))
-                {
-                    monster->flags &= ~MF_ATT_CHANGE_ATTEMPT;
-
-                    success = true;
-                }
-            }
-            // If you don't worship a good god, you make all friendly
-            // and good neutral holy beings that worship a good god
-            // hostile.
-            else if (!is_good_god(you.religion) && monster->wont_attack()
-                && is_good_god(monster->god))
+        // If you worship a good god, you get another chance to make
+        // neutral and hostile holy beings good neutral.
+        if (is_good_god(you.religion) && !mi->wont_attack())
+        {
+            if (testbits(mi->flags, MF_ATT_CHANGE_ATTEMPT))
             {
-                monster->attitude = ATT_HOSTILE;
-                monster->del_ench(ENCH_CHARM, true);
-                behaviour_event(monster, ME_ALERT, MHITYOU);
-                // For now CREATED_FRIENDLY/WAS_NEUTRAL stays.
+                mi->flags &= ~MF_ATT_CHANGE_ATTEMPT;
 
                 success = true;
             }
         }
+        // If you don't worship a good god, you make all friendly
+        // and good neutral holy beings that worship a good god
+        // hostile.
+        else if (!is_good_god(you.religion) && mi->wont_attack()
+            && is_good_god(mi->god))
+        {
+            mi->attitude = ATT_HOSTILE;
+            mi->del_ench(ENCH_CHARM, true);
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
+            // For now CREATED_FRIENDLY/WAS_NEUTRAL stays.
+
+            success = true;
+        }
     }
 
     return (success);
@@ -197,32 +196,29 @@ static bool _unholy_and_evil_beings_on_level_attitude_change()
 {
     bool success = false;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (monster->alive()
-            && (monster->is_unholy()
-                || monster->is_evil()))
-        {
+        if (!mi->is_unholy() && !mi->is_evil())
+            continue;
+
 #ifdef DEBUG_DIAGNOSTICS
-            mprf(MSGCH_DIAGNOSTICS, "Unholy/evil attitude changing: %s "
-                 "on level %d, branch %d",
-                 monster->name(DESC_PLAIN, true).c_str(),
-                 static_cast<int>(you.your_level),
-                 static_cast<int>(you.where_are_you));
+        mprf(MSGCH_DIAGNOSTICS, "Unholy/evil attitude changing: %s "
+             "on level %d, branch %d",
+             mi->name(DESC_PLAIN, true).c_str(),
+             static_cast<int>(you.your_level),
+             static_cast<int>(you.where_are_you));
 #endif
 
-            // If you worship a good god, you make all friendly and good
-            // neutral unholy and evil beings hostile.
-            if (is_good_god(you.religion) && monster->wont_attack())
-            {
-                monster->attitude = ATT_HOSTILE;
-                monster->del_ench(ENCH_CHARM, true);
-                behaviour_event(monster, ME_ALERT, MHITYOU);
-                // For now CREATED_FRIENDLY/WAS_NEUTRAL stays.
+        // If you worship a good god, you make all friendly and good
+        // neutral unholy and evil beings hostile.
+        if (is_good_god(you.religion) && mi->wont_attack())
+        {
+            mi->attitude = ATT_HOSTILE;
+            mi->del_ench(ENCH_CHARM, true);
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
+            // For now CREATED_FRIENDLY/WAS_NEUTRAL stays.
 
-                success = true;
-            }
+            success = true;
         }
     }
 
@@ -238,33 +234,30 @@ static bool _chaotic_beings_on_level_attitude_change()
 {
     bool success = false;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (monster->alive()
-            && monster->is_chaotic())
-        {
+        if (!mi->is_chaotic())
+            continue;
+
 #ifdef DEBUG_DIAGNOSTICS
-            mprf(MSGCH_DIAGNOSTICS, "Chaotic attitude changing: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
-                 static_cast<int>(you.your_level),
-                 static_cast<int>(you.where_are_you));
+        mprf(MSGCH_DIAGNOSTICS, "Chaotic attitude changing: %s on level %d, branch %d",
+             mi->name(DESC_PLAIN).c_str(),
+             static_cast<int>(you.your_level),
+             static_cast<int>(you.where_are_you));
 #endif
 
-            // If you worship Zin, you make all friendly and good neutral
-            // chaotic beings hostile.
-            if (you.religion == GOD_ZIN && monster->wont_attack())
-            {
-                monster->attitude = ATT_HOSTILE;
-                monster->del_ench(ENCH_CHARM, true);
-                behaviour_event(monster, ME_ALERT, MHITYOU);
-                // For now CREATED_FRIENDLY/WAS_NEUTRAL stays.
+        // If you worship Zin, you make all friendly and good neutral
+        // chaotic beings hostile.
+        if (you.religion == GOD_ZIN && mi->wont_attack())
+        {
+            mi->attitude = ATT_HOSTILE;
+            mi->del_ench(ENCH_CHARM, true);
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
+            // For now CREATED_FRIENDLY/WAS_NEUTRAL stays.
 
-                success = true;
-            }
+            success = true;
         }
     }
-
     return (success);
 }
 
@@ -277,30 +270,28 @@ static bool _spellcasters_on_level_attitude_change()
 {
     bool success = false;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (monster->alive()
-            && monster->is_actual_spellcaster())
-        {
+        if (!mi->is_actual_spellcaster())
+            continue;
+
 #ifdef DEBUG_DIAGNOSTICS
-            mprf(MSGCH_DIAGNOSTICS, "Spellcaster attitude changing: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
-                 static_cast<int>(you.your_level),
-                 static_cast<int>(you.where_are_you));
+        mprf(MSGCH_DIAGNOSTICS, "Spellcaster attitude changing: %s on level %d, branch %d",
+             mi->name(DESC_PLAIN).c_str(),
+             static_cast<int>(you.your_level),
+             static_cast<int>(you.where_are_you));
 #endif
 
-            // If you worship Trog, you make all friendly and good neutral
-            // magic users hostile.
-            if (you.religion == GOD_TROG && monster->wont_attack())
-            {
-                monster->attitude = ATT_HOSTILE;
-                monster->del_ench(ENCH_CHARM, true);
-                behaviour_event(monster, ME_ALERT, MHITYOU);
-                // For now CREATED_FRIENDLY/WAS_NEUTRAL stays.
+        // If you worship Trog, you make all friendly and good neutral
+        // magic users hostile.
+        if (you.religion == GOD_TROG && mi->wont_attack())
+        {
+            mi->attitude = ATT_HOSTILE;
+            mi->del_ench(ENCH_CHARM, true);
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
+            // For now CREATED_FRIENDLY/WAS_NEUTRAL stays.
 
-                success = true;
-            }
+            success = true;
         }
     }
 
@@ -322,18 +313,17 @@ static bool _make_god_gifts_on_level_disappear(bool seen = false)
                                       : GOD_NO_GOD;
     int count = 0;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (is_follower(monster)
-            && monster->has_ench(ENCH_ABJ)
-            && mons_is_god_gift(monster, god))
+        if (is_follower(*mi)
+            && mi->has_ench(ENCH_ABJ)
+            && mons_is_god_gift(*mi, god))
         {
-            if (!seen || simple_monster_message(monster, " abandons you!"))
+            if (!seen || simple_monster_message(*mi, " abandons you!"))
                 count++;
 
             // The monster disappears.
-            monster_die(monster, KILL_DISMISSED, NON_MONSTER);
+            monster_die(*mi, KILL_DISMISSED, NON_MONSTER);
         }
     }
 
@@ -366,18 +356,17 @@ static bool _make_holy_god_gifts_on_level_good_neutral(bool seen = false)
                                       : GOD_NO_GOD;
     int count = 0;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (is_follower(monster)
-            && !monster->has_ench(ENCH_CHARM)
-            && monster->is_holy()
-            && mons_is_god_gift(monster, god))
+        if (is_follower(*mi)
+            && !mi->has_ench(ENCH_CHARM)
+            && mi->is_holy()
+            && mons_is_god_gift(*mi, god))
         {
             // monster changes attitude
-            monster->attitude = ATT_GOOD_NEUTRAL;
+            mi->attitude = ATT_GOOD_NEUTRAL;
 
-            if (!seen || simple_monster_message(monster, " becomes indifferent."))
+            if (!seen || simple_monster_message(*mi, " becomes indifferent."))
                 count++;
         }
     }
@@ -412,18 +401,17 @@ static bool _make_god_gifts_on_level_hostile(bool seen = false)
                                       : GOD_NO_GOD;
     int count = 0;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (is_follower(monster)
-            && mons_is_god_gift(monster, god))
+        if (is_follower(*mi)
+            && mons_is_god_gift(*mi, god))
         {
             // monster changes attitude and behaviour
-            monster->attitude = ATT_HOSTILE;
-            monster->del_ench(ENCH_CHARM, true);
-            behaviour_event(monster, ME_ALERT, MHITYOU);
+            mi->attitude = ATT_HOSTILE;
+            mi->del_ench(ENCH_CHARM, true);
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
 
-            if (!seen || simple_monster_message(monster, " turns against you!"))
+            if (!seen || simple_monster_message(*mi, " turns against you!"))
                 count++;
         }
     }
@@ -457,33 +445,32 @@ static bool _yred_slaves_on_level_abandon_you()
 {
     bool success = false;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (_is_yred_enslaved_body_and_soul(monster))
+        if (_is_yred_enslaved_body_and_soul(*mi))
         {
 #ifdef DEBUG_DIAGNOSTICS
             mprf(MSGCH_DIAGNOSTICS, "Undead soul abandoning: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
+                 mi->name(DESC_PLAIN).c_str(),
                  static_cast<int>(you.your_level),
                  static_cast<int>(you.where_are_you));
 #endif
 
-            yred_make_enslaved_soul(monster, true, true, true);
+            yred_make_enslaved_soul(*mi, true, true, true);
 
             success = true;
         }
-        else if (is_yred_undead_slave(monster))
+        else if (is_yred_undead_slave(*mi))
         {
 #ifdef DEBUG_DIAGNOSTICS
             mprf(MSGCH_DIAGNOSTICS, "Undead abandoning: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
+                 mi->name(DESC_PLAIN).c_str(),
                  static_cast<int>(you.your_level),
                  static_cast<int>(you.where_are_you));
 #endif
 
-            monster->attitude = ATT_HOSTILE;
-            behaviour_event(monster, ME_ALERT, MHITYOU);
+            mi->attitude = ATT_HOSTILE;
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
             // For now CREATED_FRIENDLY stays.
 
             success = true;
@@ -499,20 +486,19 @@ static bool _beogh_followers_on_level_abandon_you()
 
     // Note that orc high priests' summons are gifts of Beogh, so we
     // can't use is_orcish_follower() here.
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (mons_is_god_gift(monster, GOD_BEOGH))
+        if (mons_is_god_gift(*mi, GOD_BEOGH))
         {
 #ifdef DEBUG_DIAGNOSTICS
             mprf(MSGCH_DIAGNOSTICS, "Orc abandoning: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
+                 mi->name(DESC_PLAIN).c_str(),
                  static_cast<int>(you.your_level),
                  static_cast<int>(you.where_are_you));
 #endif
 
-            monster->attitude = ATT_HOSTILE;
-            behaviour_event(monster, ME_ALERT, MHITYOU);
+            mi->attitude = ATT_HOSTILE;
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
             // For now CREATED_FRIENDLY stays.
 
             success = true;
@@ -526,20 +512,19 @@ static bool _jiyva_slimes_on_level_abandon_you()
 {
     bool success = false;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (is_fellow_slime(monster))
+        if (is_fellow_slime(*mi))
         {
 #ifdef DEBUG_DIAGNOSTICS
             mprf(MSGCH_DIAGNOSTICS, "Slime abandoning: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
+                 mi->name(DESC_PLAIN).c_str(),
                  static_cast<int>(you.your_level),
                  static_cast<int>(you.where_are_you));
 #endif
 
-            monster->attitude = ATT_HOSTILE;
-            behaviour_event(monster, ME_ALERT, MHITYOU);
+            mi->attitude = ATT_HOSTILE;
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
             // For now WAS_NEUTRAL stays.
 
             success = true;
@@ -625,27 +610,25 @@ bool yred_slaves_abandon_you()
 
 static bool _fedhas_plants_on_level_hostile()
 {
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (monster->alive()
-            && mons_is_plant(monster))
+        if (mons_is_plant(*mi))
         {
 #ifdef DEBUG_DIAGNOSTICS
             mprf(MSGCH_DIAGNOSTICS, "Plant hostility: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
+                 mi->name(DESC_PLAIN).c_str(),
                  static_cast<int>(you.your_level),
                  static_cast<int>(you.where_are_you));
 #endif
 
             // You can potentially turn an oklob or whatever neutral
             // again by going back to Fedhas.
-            if (testbits(monster->flags, MF_ATT_CHANGE_ATTEMPT))
-                monster->flags &= ~MF_ATT_CHANGE_ATTEMPT;
+            if (testbits(mi->flags, MF_ATT_CHANGE_ATTEMPT))
+                mi->flags &= ~MF_ATT_CHANGE_ATTEMPT;
 
-            monster->attitude = ATT_HOSTILE;
-            monster->del_ench(ENCH_CHARM, true);
-            behaviour_event(monster, ME_ALERT, MHITYOU);
+            mi->attitude = ATT_HOSTILE;
+            mi->del_ench(ENCH_CHARM, true);
+            behaviour_event(*mi, ME_ALERT, MHITYOU);
             // For now WAS_NEUTRAL stays.
         }
     }
diff --git a/crawl-ref/source/beam.cc b/crawl-ref/source/beam.cc
index 8a10cc4531..8203461539 100644
--- a/crawl-ref/source/beam.cc
+++ b/crawl-ref/source/beam.cc
@@ -45,6 +45,7 @@
 #include "message.h"
 #include "misc.h"
 #include "mon-behv.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monstuff.h"
 #include "mon-util.h"
@@ -2610,26 +2611,18 @@ bool mass_enchantment( enchant_type wh_enchant, int pow, int origin,
 
     const kill_category kc = (origin == MHITYOU ? KC_YOU : KC_OTHER);
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi(&you.get_los()); mi; ++mi)
     {
-        monsters* const monster = &menv[i];
-
-        if (!monster->alive())
-            continue;
-
-        if (!mons_near(monster))
-            continue;
-
-        if (monster->has_ench(wh_enchant))
+        if (mi->has_ench(wh_enchant))
             continue;
 
         if (m_attempted)
             ++*m_attempted;
 
-        if (_monster_resists_mass_enchantment(monster, wh_enchant, pow))
+        if (_monster_resists_mass_enchantment(*mi, wh_enchant, pow))
             continue;
 
-        if (monster->add_ench(mon_enchant(wh_enchant, 0, kc)))
+        if (mi->add_ench(mon_enchant(wh_enchant, 0, kc)))
         {
             if (m_succumbed)
                 ++*m_succumbed;
@@ -2644,11 +2637,11 @@ bool mass_enchantment( enchant_type wh_enchant, int pow, int origin,
             default:             msg = NULL;                      break;
             }
             if (msg)
-                msg_generated = simple_monster_message(monster, msg);
+                msg_generated = simple_monster_message(*mi, msg);
 
             // Extra check for fear (monster needs to reevaluate behaviour).
             if (wh_enchant == ENCH_FEAR)
-                behaviour_event(monster, ME_SCARE, origin);
+                behaviour_event(*mi, ME_SCARE, origin);
         }
     }
 
diff --git a/crawl-ref/source/decks.cc b/crawl-ref/source/decks.cc
index e82ba90e70..cdd4626e99 100644
--- a/crawl-ref/source/decks.cc
+++ b/crawl-ref/source/decks.cc
@@ -31,6 +31,7 @@
 #include "maps.h"
 #include "message.h"
 #include "misc.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monstuff.h"
 #include "mutation.h"
@@ -2513,16 +2514,13 @@ static void _crusade_card(int power, deck_rarity_type rarity)
     if (power_level >= 1)
     {
         // A chance to convert opponents.
-        for (int i = 0; i < MAX_MONSTERS; ++i)
+        for (monster_iterator mi(&you.get_los()); mi; ++mi)
         {
-            monsters* const monster = &menv[i];
-            if (!monster->alive()
-                || !mons_near(monster)
-                || monster->friendly()
-                || monster->holiness() != MH_NATURAL
-                || mons_is_unique(monster->type)
-                || mons_immune_magic(monster)
-                || player_will_anger_monster(monster))
+             if (mi->friendly()
+                || mi->holiness() != MH_NATURAL
+                || mons_is_unique(mi->type)
+                || mons_immune_magic(*mi)
+                || player_will_anger_monster(*mi))
             {
                 continue;
             }
@@ -2531,35 +2529,35 @@ static void _crusade_card(int power, deck_rarity_type rarity)
             // (though not immunity) check.  Specifically,
             // you can convert Killer Klowns this way.
             // Might be too good.
-            if (monster->hit_dice * 35 < random2(power))
+            if (mi->hit_dice * 35 < random2(power))
             {
-                simple_monster_message(monster, " is converted.");
+                simple_monster_message(*mi, " is converted.");
 
                 if (one_chance_in(5 - power_level))
                 {
-                    monster->attitude = ATT_FRIENDLY;
+                    mi->attitude = ATT_FRIENDLY;
 
                     // If you worship a god that lets you recruit
                     // permanent followers, or a god allied with one,
                     // count this as a recruitment.
                     if (is_good_god(you.religion)
                         || you.religion == GOD_BEOGH
-                            && mons_species(monster->type) == MONS_ORC
-                            && !monster->is_summoned()
-                            && !monster->is_shapeshifter())
+                            && mons_species(mi->type) == MONS_ORC
+                            && !mi->is_summoned()
+                            && !mi->is_shapeshifter())
                     {
                         // Prevent assertion if the monster was
                         // previously worshipping a different god,
                         // rather than already worshipping your god or
                         // being an atheist.
-                        monster->god = GOD_NO_GOD;
+                        mi->god = GOD_NO_GOD;
 
-                        mons_make_god_gift(monster, is_good_god(you.religion) ?
+                        mons_make_god_gift(*mi, is_good_god(you.religion) ?
                                            GOD_SHINING_ONE : GOD_BEOGH);
                     }
                 }
                 else
-                    monster->add_ench(ENCH_CHARM);
+                    mi->add_ench(ENCH_CHARM);
             }
         }
     }
diff --git a/crawl-ref/source/effects.cc b/crawl-ref/source/effects.cc
index 195aaa9792..a9eb9ceee6 100644
--- a/crawl-ref/source/effects.cc
+++ b/crawl-ref/source/effects.cc
@@ -43,6 +43,7 @@
 #include "misc.h"
 #include "mon-behv.h"
 #include "mon-cast.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monstuff.h"
 #include "mon-util.h"
@@ -2449,44 +2450,35 @@ bool recharge_wand(int item_slot)
     return (false);
 }
 
+// Berserking monsters cannot be ordered around.
+static bool _follows_orders(monsters* mon)
+{
+    return (mon->friendly() && mon->type != MONS_GIANT_SPORE
+        && !mon->berserk());
+}
+
 // Sets foe target of friendly monsters.
 // If allow_patrol is true, patrolling monsters get MHITNOT instead.
 static void _set_friendly_foes(bool allow_patrol = false)
 {
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi(&you.get_los()); mi; ++mi)
     {
-        monsters *mon(&menv[i]);
-        if (!mon->alive() || !mons_near(mon) || !mon->friendly()
-            || mon->type == MONS_GIANT_SPORE)
-        {
+        if (!_follows_orders(*mi))
             continue;
-        }
-
-        // Berserking monsters cannot be ordered around.
-        if (mon->berserk())
-            continue;
-
-        mon->foe = (allow_patrol && mon->is_patrolling() ? MHITNOT
+        mi->foe = (allow_patrol && mi->is_patrolling() ? MHITNOT
                                                          : you.pet_target);
     }
 }
 
 static void _set_allies_patrol_point(bool clear = false)
 {
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi(&you.get_los()); mi; ++mi)
     {
-        monsters *mon(&menv[i]);
-        if (!mon->alive() || !mons_near(mon) || !mon->friendly())
+        if (!_follows_orders(*mi))
             continue;
-
-        // Berserking monsters cannot be ordered around.
-        if (mon->berserk() || mon->type == MONS_GIANT_SPORE)
-            continue;
-
-        mon->patrol_point = (clear ? coord_def(0, 0) : mon->pos());
-
+        mi->patrol_point = (clear ? coord_def(0, 0) : mi->pos());
         if (!clear)
-            mon->behaviour = BEH_WANDER;
+            mi->behaviour = BEH_WANDER;
     }
 }
 
@@ -4166,57 +4158,52 @@ void update_level(double elapsedTime)
     dungeon_events.fire_event(
         dgn_event(DET_TURN_ELAPSED, coord_def(0, 0), turns * 10));
 
-    for (int m = 0; m < MAX_MONSTERS; m++)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *mon = &menv[m];
-
-        if (!mon->alive())
-            continue;
-
 #if DEBUG_DIAGNOSTICS
         mons_total++;
 #endif
 
         // Pacified monsters often leave the level now.
-        if (mon->pacified() && turns > random2(40) + 21)
+        if (mi->pacified() && turns > random2(40) + 21)
         {
-            make_mons_leave_level(mon);
+            make_mons_leave_level(*mi);
             continue;
         }
 
         // Following monsters don't get movement.
-        if (mon->flags & MF_JUST_SUMMONED)
+        if (mi->flags & MF_JUST_SUMMONED)
             continue;
 
         // XXX: Allow some spellcasting (like Healing and Teleport)? - bwr
-        // const bool healthy = (mon->hit_points * 2 > mon->max_hit_points);
+        // const bool healthy = (mi->hit_points * 2 > mi->max_hit_points);
 
         // This is the monster healing code, moved here from tag.cc:
-        if (mons_can_regenerate(mon))
+        if (mons_can_regenerate(*mi))
         {
-            if (monster_descriptor(mon->type, MDSC_REGENERATES)
-                || mon->type == MONS_PLAYER_GHOST)
+            if (monster_descriptor(mi->type, MDSC_REGENERATES)
+                || mi->type == MONS_PLAYER_GHOST)
             {
-                mon->heal(turns);
+                mi->heal(turns);
             }
             else
             {
                 // Set a lower ceiling of 0.1 on the regen rate.
                 const int regen_rate =
-                    std::max(mons_natural_regen_rate(mon) * 2, 5);
+                    std::max(mons_natural_regen_rate(*mi) * 2, 5);
 
-                mon->heal(div_rand_round(turns * regen_rate, 50));
+                mi->heal(div_rand_round(turns * regen_rate, 50));
             }
         }
 
         // Handle nets specially to remove the trapping property of the net.
-        if (mon->caught())
-            mon->del_ench(ENCH_HELD, true);
+        if (mi->caught())
+            mi->del_ench(ENCH_HELD, true);
 
-        _catchup_monster_moves(mon, turns);
+        _catchup_monster_moves(*mi, turns);
 
-        if (turns >= 10 && mon->alive())
-            mon->timeout_enchantments(turns / 10);
+        if (turns >= 10 && mi->alive())
+            mi->timeout_enchantments(turns / 10);
     }
 
 #if DEBUG_DIAGNOSTICS
diff --git a/crawl-ref/source/ghost.cc b/crawl-ref/source/ghost.cc
index 901a4b92d4..1886b65f8b 100644
--- a/crawl-ref/source/ghost.cc
+++ b/crawl-ref/source/ghost.cc
@@ -16,6 +16,7 @@
 #include "externs.h"
 #include "itemname.h"
 #include "itemprop.h"
+#include "mon-iter.h"
 #include "ng-input.h"
 #include "random.h"
 #include "skills2.h"
@@ -846,16 +847,13 @@ void ghost_demon::announce_ghost(const ghost_demon &g)
 
 void ghost_demon::find_extra_ghosts( std::vector<ghost_demon> &gs, int n )
 {
-    for (int i = 0; n > 0 && i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        if (!menv[i].alive())
-            continue;
-
-        if (menv[i].type == MONS_PLAYER_GHOST && menv[i].ghost.get())
+        if (mi->type == MONS_PLAYER_GHOST && mi->ghost.get())
         {
             // Bingo!
-            announce_ghost(*menv[i].ghost);
-            gs.push_back(*menv[i].ghost);
+            announce_ghost(*(mi->ghost));
+            gs.push_back(*(mi->ghost));
             --n;
         }
     }
diff --git a/crawl-ref/source/godabil.cc b/crawl-ref/source/godabil.cc
index a7f4c77484..a017265ad9 100644
--- a/crawl-ref/source/godabil.cc
+++ b/crawl-ref/source/godabil.cc
@@ -23,6 +23,7 @@
 #include "misc.h"
 #include "mon-act.h"
 #include "mon-behv.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monstuff.h"
 #include "mon-util.h"
@@ -203,22 +204,21 @@ static bool _yred_enslaved_souls_on_level_disappear()
 {
     bool success = false;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (_is_yred_enslaved_soul(monster))
+        if (_is_yred_enslaved_soul(*mi))
         {
 #ifdef DEBUG_DIAGNOSTICS
             mprf(MSGCH_DIAGNOSTICS, "Undead soul disappearing: %s on level %d, branch %d",
-                 monster->name(DESC_PLAIN).c_str(),
+                 mi->name(DESC_PLAIN).c_str(),
                  static_cast<int>(you.your_level),
                  static_cast<int>(you.where_are_you));
 #endif
 
-            simple_monster_message(monster, " is freed.");
+            simple_monster_message(*mi, " is freed.");
 
             // The monster disappears.
-            monster_die(monster, KILL_DISMISSED, NON_MONSTER);
+            monster_die(*mi, KILL_DISMISSED, NON_MONSTER);
 
             success = true;
         }
diff --git a/crawl-ref/source/misc.cc b/crawl-ref/source/misc.cc
index 0c4d997d89..d1744552bb 100644
--- a/crawl-ref/source/misc.cc
+++ b/crawl-ref/source/misc.cc
@@ -56,6 +56,7 @@
 #include "mapmark.h"
 #include "message.h"
 #include "monplace.h"
+#include "mon-iter.h"
 #include "mon-util.h"
 #include "monstuff.h"
 #include "ouch.h"
@@ -2968,14 +2969,11 @@ static void monster_threat_values(double *general, double *highest,
     double sum = 0;
     int highest_xp = -1;
 
-    monsters *monster = NULL;
-    for (int it = 0; it < MAX_MONSTERS; it++)
+    for (monster_iterator mi(&you.get_los()); mi; ++mi)
     {
-        monster = &menv[it];
-
-        if (monster->alive() && mons_near(monster) && !monster->friendly())
+        if (!mi->friendly())
         {
-            const int xp = exper_value(monster);
+            const int xp = exper_value(*mi);
             const double log_xp = log((double)xp);
             sum += log_xp;
             if (xp > highest_xp)
@@ -2983,7 +2981,7 @@ static void monster_threat_values(double *general, double *highest,
                 highest_xp = xp;
                 *highest   = log_xp;
             }
-            if (!you.can_see(monster))
+            if (!you.can_see(*mi))
                 *invis = true;
         }
     }
diff --git a/crawl-ref/source/mon-abil.cc b/crawl-ref/source/mon-abil.cc
index 7067112d6e..bfc77357b8 100644
--- a/crawl-ref/source/mon-abil.cc
+++ b/crawl-ref/source/mon-abil.cc
@@ -24,6 +24,7 @@
 #include "mon-act.h"
 #include "mon-behv.h"
 #include "mon-cast.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monspeak.h"
 #include "monstuff.h"
@@ -591,44 +592,41 @@ static bool _orc_battle_cry(monsters *chief)
         const int boss_index = monster_index(chief);
         const int level = chief->hit_dice > 12? 2 : 1;
         std::vector<monsters*> seen_affected;
-        for (int i = 0; i < MAX_MONSTERS; ++i)
+        for (monster_iterator mi(chief); mi; ++mi)
         {
-            monsters *mon = &menv[i];
-            if (mon != chief
-                && mon->alive()
-                && mons_species(mon->type) == MONS_ORC
-                && mons_aligned(boss_index, i)
-                && mon->hit_dice < chief->hit_dice
-                && !mon->berserk()
-                && !mon->has_ench(ENCH_MIGHT)
-                && !mon->cannot_move()
-                && !mon->confused()
-                && chief->can_see(mon))
+            if (*mi != chief
+                && mons_species(mi->type) == MONS_ORC
+                && mons_aligned(boss_index, mi->mindex())
+                && mi->hit_dice < chief->hit_dice
+                && !mi->berserk()
+                && !mi->has_ench(ENCH_MIGHT)
+                && !mi->cannot_move()
+                && !mi->confused())
             {
-                mon_enchant ench = mon->get_ench(ENCH_BATTLE_FRENZY);
+                mon_enchant ench = mi->get_ench(ENCH_BATTLE_FRENZY);
                 if (ench.ench == ENCH_NONE || ench.degree < level)
                 {
                     const int dur =
-                        random_range(12, 20) * speed_to_duration(mon->speed);
+                        random_range(12, 20) * speed_to_duration(mi->speed);
 
                     if (ench.ench != ENCH_NONE)
                     {
                         ench.degree   = level;
                         ench.duration = std::max(ench.duration, dur);
-                        mon->update_ench(ench);
+                        mi->update_ench(ench);
                     }
                     else
                     {
-                        mon->add_ench(mon_enchant(ENCH_BATTLE_FRENZY, level,
+                        mi->add_ench(mon_enchant(ENCH_BATTLE_FRENZY, level,
                                                   KC_OTHER, dur));
                     }
 
                     affected++;
-                    if (you.can_see(mon))
-                        seen_affected.push_back(mon);
+                    if (you.can_see(*mi))
+                        seen_affected.push_back(*mi);
 
-                    if (mon->asleep())
-                        behaviour_event(mon, ME_DISTURB, MHITNOT, chief->pos());
+                    if (mi->asleep())
+                        behaviour_event(*mi, ME_DISTURB, MHITNOT, chief->pos());
                 }
             }
         }
@@ -729,23 +727,20 @@ static bool _moth_incite_monsters(const monsters *mon)
         return false;
 
     int goaded = 0;
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    circle_def c(mon->pos(), 3, C_SQUARE);
+    for (monster_iterator mi(&c); mi; ++mi)
     {
-        monsters *targ = &menv[i];
-        if (targ == mon || !targ->alive() || !targ->needs_berserk())
+        if (*mi == mon || !mi->needs_berserk())
             continue;
 
-        if (mon->pos().distance_from(targ->pos()) > 3)
-            continue;
-
-        if (is_sanctuary(targ->pos()))
+        if (is_sanctuary(mi->pos()))
             continue;
 
         // Cannot goad other moths of wrath!
-        if (targ->type == MONS_MOTH_OF_WRATH)
+        if (mi->type == MONS_MOTH_OF_WRATH)
             continue;
 
-        if (_make_monster_angry(mon, targ) && !one_chance_in(3 * ++goaded))
+        if (_make_monster_angry(mon, *mi) && !one_chance_in(3 * ++goaded))
             return (true);
     }
 
@@ -779,6 +774,7 @@ bool mon_special_ability(monsters *monster, bolt & beem)
 
     spell_type spell = SPELL_NO_SPELL;
 
+    circle_def c;
     switch (mclass)
     {
     case MONS_UGLY_THING:
@@ -832,16 +828,9 @@ bool mon_special_ability(monsters *monster, bolt & beem)
             break;
         }
 
-        for (int i = 0; i < MAX_MONSTERS; i++)
+        c = circle_def(monster->pos(), 4, C_CIRCLE);
+        for (monster_iterator targ(&c); targ; ++targ)
         {
-            monsters *targ = &menv[i];
-
-            if (targ->type == MONS_NO_MONSTER)
-                continue;
-
-            if (distance(monster->pos(), targ->pos()) >= 5)
-                continue;
-
             if (mons_atts_aligned(monster->attitude, targ->attitude))
                 continue;
 
diff --git a/crawl-ref/source/mon-act.cc b/crawl-ref/source/mon-act.cc
index e0b9dfbe94..0f17f8c53b 100644
--- a/crawl-ref/source/mon-act.cc
+++ b/crawl-ref/source/mon-act.cc
@@ -31,6 +31,7 @@
 #include "mon-abil.h"
 #include "mon-behv.h"
 #include "mon-cast.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monstuff.h"
 #include "mutation.h"
@@ -2077,20 +2078,18 @@ void handle_monsters()
     // them to move again.
     memset(immobile_monster, 0, sizeof immobile_monster);
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-
-        if (!monster->alive() || immobile_monster[i])
+        if (immobile_monster[mi->mindex()])
             continue;
 
-        const coord_def oldpos = monster->pos();
+        const coord_def oldpos = mi->pos();
 
-        monster->update_los();
-        _handle_monster_move(monster);
+        mi->update_los();
+        _handle_monster_move(*mi);
 
-        if (!invalid_monster(monster) && monster->pos() != oldpos)
-            immobile_monster[i] = true;
+        if (!invalid_monster(*mi) && mi->pos() != oldpos)
+            immobile_monster[mi->mindex()] = true;
 
         // If the player got banished, discard pending monster actions.
         if (you.banished)
diff --git a/crawl-ref/source/monstuff.cc b/crawl-ref/source/monstuff.cc
index 6c849a2ba6..3e37144226 100644
--- a/crawl-ref/source/monstuff.cc
+++ b/crawl-ref/source/monstuff.cc
@@ -34,6 +34,7 @@
 #include "message.h"
 #include "misc.h"
 #include "mon-behv.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monspeak.h"
 #include "notes.h"
@@ -1269,18 +1270,17 @@ void pikel_band_neutralise ()
     // with MF_BAND_MEMBER are Pikel's band members.
     bool message_made = false;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (monster->alive() && monster->type == MONS_HUMAN
-            && testbits(monster->flags, MF_BAND_MEMBER))
+        if (mi->type == MONS_HUMAN
+            && testbits(mi->flags, MF_BAND_MEMBER))
         {
-            if (monster->observable() && !message_made)
+            if (mi->observable() && !message_made)
             {
                 mpr("Pikel's slaves thank you for their freedom.");
                 message_made = true;
             }
-            mons_pacify(monster);
+            mons_pacify(*mi);
         }
     }
 }
@@ -1296,60 +1296,59 @@ static void _hogs_to_humans()
     //        porkalator spell, they should be handled specially...
     int any = 0, human = 0;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (monster->alive() && monster->type == MONS_HOG)
-        {
-            const bool could_see = you.can_see(monster);
+        if (!mi->type == MONS_HOG)
+            continue;
 
-            // XXX: This resets the size of slime creatures, the number
-            // of heads a hydra has, and the number of spikes a manticore
-            // has.  Plus it also changes the colour of a draconian which
-            // has a sub-type.  And it re-rolls the spellbook the monster
-            // has.
-            if (monster->number == 0)
-                monster->type = MONS_HUMAN;
-            else
-                monster->type = (monster_type) (monster->number - 1);
+        const bool could_see = you.can_see(*mi);
 
-            monster->number = 0;
-            define_monster(*monster);
+        // XXX: This resets the size of slime creatures, the number
+        // of heads a hydra has, and the number of spikes a manticore
+        // has.  Plus it also changes the colour of a draconian which
+        // has a sub-type.  And it re-rolls the spellbook the monster
+        // has.
+        if (mi->number == 0)
+            mi->type = MONS_HUMAN;
+        else
+            mi->type = (monster_type) (mi->number - 1);
 
-            const bool can_see = you.can_see(monster);
+        mi->number = 0;
+        define_monster(**mi);
 
-            // A monster changing factions while in the arena messes up
-            // arena book-keeping.
-            if (!crawl_state.arena)
+        const bool can_see = you.can_see(*mi);
+
+        // A monster changing factions while in the arena messes up
+        // arena book-keeping.
+        if (!crawl_state.arena)
+        {
+            // * A monster's attitude shouldn't downgrade from friendly
+            //   or good-neutral because you helped it.  It'd suck to
+            //   lose a permanent ally that way.
+            //
+            // * A monster has to be smart enough to realize that you
+            //   helped it.
+            if (mi->attitude == ATT_HOSTILE
+                && mons_intel(*mi) >= I_NORMAL)
             {
-                // * A monster's attitude shouldn't downgrade from friendly
-                //   or good-neutral because you helped it.  It'd suck to
-                //   lose a permanent ally that way.
-                //
-                // * A monster has to be smart enough to realize that you
-                //   helped it.
-                if (monster->attitude == ATT_HOSTILE
-                    && mons_intel(monster) >= I_NORMAL)
-                {
-                    monster->attitude = ATT_GOOD_NEUTRAL;
-                    monster->flags |= MF_WAS_NEUTRAL;
-                }
+                mi->attitude = ATT_GOOD_NEUTRAL;
+                mi->flags |= MF_WAS_NEUTRAL;
             }
+        }
 
-            behaviour_event(monster, ME_EVAL);
+        behaviour_event(*mi, ME_EVAL);
 
-            if (could_see && can_see)
-            {
-                any++;
-                if (monster->type == MONS_HUMAN)
-                    human++;
-            }
-            else if (could_see && !can_see)
-                mpr("The hog vanishes!");
-            else if (!could_see && can_see)
-                mprf("%s appears from out of thin air!",
-                     monster->name(DESC_CAP_A).c_str());
+        if (could_see && can_see)
+        {
+            any++;
+            if (mi->type == MONS_HUMAN)
+                human++;
         }
+        else if (could_see && !can_see)
+            mpr("The hog vanishes!");
+        else if (!could_see && can_see)
+            mprf("%s appears from out of thin air!",
+                 mi->name(DESC_CAP_A).c_str());
     }
 
     if (any == 1)
@@ -1393,14 +1392,13 @@ void mons_relocated(monsters *monster)
         if (invalid_monster_index(headnum))
             return;
 
-        for (int i = 0; i < MAX_MONSTERS; ++i)
+        for (monster_iterator mi; mi; ++mi)
         {
-            monsters *tentacle = &menv[i];
-            if (tentacle->type == MONS_KRAKEN_TENTACLE
-                && (int)tentacle->number == headnum
-                && _tentacle_too_far(monster, tentacle))
+            if (mi->type == MONS_KRAKEN_TENTACLE
+                && (int)mi->number == headnum
+                && _tentacle_too_far(monster, *mi))
             {
-                monster_die(tentacle, KILL_RESET, -1, true, false);
+                monster_die(*mi, KILL_RESET, -1, true, false);
             }
         }
     }
@@ -1423,15 +1421,14 @@ static int _destroy_tentacles(monsters *head)
     if (invalid_monster_index(headnum))
         return 0;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[i];
-        if (monster->type == MONS_KRAKEN_TENTACLE
-            && (int)monster->number == headnum)
+        if (mi->type == MONS_KRAKEN_TENTACLE
+            && (int)mi->number == headnum)
         {
-            if (mons_near(monster))
+            if (mons_near(*mi))
                 tent++;
-            monster->hurt(monster, INSTANT_DEATH);
+            mi->hurt(*mi, INSTANT_DEATH);
         }
     }
     return tent;
@@ -2199,9 +2196,9 @@ void monster_cleanup(monsters *monster)
     unsigned int monster_killed = monster_index(monster);
     monster->reset();
 
-    for (int dmi = 0; dmi < MAX_MONSTERS; dmi++)
-        if (menv[dmi].foe == monster_killed)
-            menv[dmi].foe = MHITNOT;
+    for (monster_iterator mi; mi; ++mi)
+       if (mi->foe == monster_killed)
+            mi->foe = MHITNOT;
 
     if (you.pet_target == monster_killed)
         you.pet_target = MHITNOT;
@@ -2210,24 +2207,14 @@ void monster_cleanup(monsters *monster)
 // If you're invis and throw/zap whatever, alerts menv to your position.
 void alert_nearby_monsters(void)
 {
-    monsters *monster = 0;       // NULL {dlb}
-
-    for (int it = 0; it < MAX_MONSTERS; it++)
-    {
-        monster = &menv[it];
-
-        // Judging from the above comment, this function isn't
-        // intended to wake up monsters, so we're only going to
-        // alert monsters that aren't sleeping.  For cases where an
-        // event should wake up monsters and alert them, I'd suggest
-        // calling noisy() before calling this function. -- bwr
-        if (monster->alive()
-            && mons_near(monster)
-            && !monster->asleep())
-        {
-            behaviour_event(monster, ME_ALERT, MHITYOU);
-        }
-    }
+    // Judging from the above comment, this function isn't
+    // intended to wake up monsters, so we're only going to
+    // alert monsters that aren't sleeping.  For cases where an
+    // event should wake up monsters and alert them, I'd suggest
+    // calling noisy() before calling this function. -- bwr
+    for (monster_iterator mi(&you.get_los()); mi; ++mi)
+        if (!mi->asleep())
+             behaviour_event(*mi, ME_ALERT, MHITYOU);
 }
 
 static bool _valid_morph(monsters *monster, monster_type new_mclass)
@@ -3620,15 +3607,14 @@ int dismiss_monsters(std::string pattern) {
     // Dismiss by regex
     text_pattern tpat(pattern);
     int ndismissed = 0;
-    for (int mon = 0; mon < MAX_MONSTERS; mon++)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[mon];
-        if (monster->alive() &&
-            (tpat.empty() || tpat.matches(monster->name(DESC_PLAIN, true))))
+        if (mi->alive() &&
+            (tpat.empty() || tpat.matches(mi->name(DESC_PLAIN, true))))
         {
             if (!keep_item)
-                _vanish_orig_eq(monster);
-            monster_die(monster, KILL_DISMISSED, NON_MONSTER, false, true);
+                _vanish_orig_eq(*mi);
+            monster_die(*mi, KILL_DISMISSED, NON_MONSTER, false, true);
             ++ndismissed;
         }
     }
diff --git a/crawl-ref/source/spells3.cc b/crawl-ref/source/spells3.cc
index 97b2cb04d0..edca2202c5 100644
--- a/crawl-ref/source/spells3.cc
+++ b/crawl-ref/source/spells3.cc
@@ -35,6 +35,7 @@
 #include "message.h"
 #include "misc.h"
 #include "mon-behv.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monstuff.h"
 #include "mon-util.h"
@@ -1767,12 +1768,8 @@ bool remove_sanctuary(bool did_attack)
 
     // Now that the sanctuary is gone, monsters aren't afraid of it
     // anymore.
-    for (int i = 0; i < MAX_MONSTERS; ++i)
-    {
-        monsters *mon = &menv[i];
-        if (mon->alive())
-            mons_stop_fleeing_from_sanctuary(mon);
-    }
+    for (monster_iterator mi; mi; ++mi)
+        mons_stop_fleeing_from_sanctuary(*mi);
 
     if (is_resting())
         stop_running();
diff --git a/crawl-ref/source/view.cc b/crawl-ref/source/view.cc
index c0a55da171..3ee1f5e6bb 100644
--- a/crawl-ref/source/view.cc
+++ b/crawl-ref/source/view.cc
@@ -48,6 +48,7 @@
 #include "message.h"
 #include "misc.h"
 #include "mon-behv.h"
+#include "mon-iter.h"
 #include "monplace.h"
 #include "monstuff.h"
 #include "mon-util.h"
@@ -122,34 +123,31 @@ void flush_comes_into_view()
 
 void monster_grid_updates()
 {
-    for (int s = 0; s < MAX_MONSTERS; ++s)
+    for (monster_iterator mi(&you.get_los()); mi; ++mi)
     {
-        monsters *monster = &menv[s];
-
-        if (monster->alive() && mons_near(monster))
+        if ((mi->asleep() || mons_is_wandering(*mi))
+            && check_awaken(*mi))
         {
-            if ((monster->asleep() || mons_is_wandering(monster))
-                && check_awaken(monster))
-            {
-                behaviour_event(monster, ME_ALERT, MHITYOU, you.pos(), false);
-                handle_monster_shouts(monster);
-            }
+            behaviour_event(*mi, ME_ALERT, MHITYOU, you.pos(), false);
+            handle_monster_shouts(*mi);
+        }
 
-            if (!monster->visible_to(&you))
-                continue;
+        if (!mi->visible_to(&you))
+            continue;
 
-            good_god_follower_attitude_change(monster);
-            beogh_follower_convert(monster);
-            slime_convert(monster);
-            fedhas_neutralise(monster);
-        }
+        good_god_follower_attitude_change(*mi);
+        beogh_follower_convert(*mi);
+        slime_convert(*mi);
+        fedhas_neutralise(*mi);
     }
 }
 
-static void _check_monster_pos(const monsters* monster, int s)
+static void _check_monster_pos(const monsters* monster)
 {
+    int s = monster->mindex();
     ASSERT(mgrd(monster->pos()) == s);
 
+    // [rob] The following in case asserts aren't enabled.
     // [enne] - It's possible that mgrd and monster->x/y are out of
     // sync because they are updated separately.  If we can see this
     // monster, then make sure that the mgrd is set correctly.
@@ -169,20 +167,15 @@ static void _check_monster_pos(const monsters* monster, int s)
 
 void monster_grid()
 {
-    for (int s = 0; s < MAX_MONSTERS; ++s)
+    for (monster_iterator mi(&you.get_los()); mi; ++mi)
     {
-        monsters *monster = &menv[s];
-
-        if (monster->alive() && mons_near(monster))
-        {
-            _check_monster_pos(monster, s);
-            env.show.update_monster(monster);
+        _check_monster_pos(*mi);
+        env.show.update_monster(*mi);
 
 #ifdef USE_TILE
-            if (monster->visible_to(&you))
-                tile_place_monster(monster->pos().x, monster->pos().y, s, true);
+        if (mi->visible_to(&you))
+            tile_place_monster(mi->pos().x, mi->pos().y, s, true);
 #endif
-        }
     }
 }
 
@@ -190,39 +183,34 @@ void update_monsters_in_view()
 {
     unsigned int num_hostile = 0;
 
-    for (int s = 0; s < MAX_MONSTERS; s++)
+    for (monster_iterator mi; mi; ++mi)
     {
-        monsters *monster = &menv[s];
-
-        if (!monster->alive())
-            continue;
-
-        if (mons_near(monster))
+        if (mons_near(*mi))
         {
-            if (monster->attitude == ATT_HOSTILE)
+            if (mi->attitude == ATT_HOSTILE)
                 num_hostile++;
 
-            if (mons_is_unknown_mimic(monster))
+            if (mons_is_unknown_mimic(*mi))
             {
                 // For unknown mimics, don't mark as seen,
                 // but do mark it as in view for later messaging.
                 // FIXME: is this correct?
-                monster->flags |= MF_WAS_IN_VIEW;
+                mi->flags |= MF_WAS_IN_VIEW;
             }
-            else if (monster->visible_to(&you))
+            else if (mi->visible_to(&you))
             {
-                handle_seen_interrupt(monster);
-                seen_monster(monster);
+                handle_seen_interrupt(*mi);
+                seen_monster(*mi);
             }
             else
-                monster->flags &= ~MF_WAS_IN_VIEW;
+                mi->flags &= ~MF_WAS_IN_VIEW;
         }
         else
-            monster->flags &= ~MF_WAS_IN_VIEW;
+            mi->flags &= ~MF_WAS_IN_VIEW;
 
         // If the monster hasn't been seen by the time that the player
         // gets control back then seen_context is out of date.
-        monster->seen_context.clear();
+        mi->seen_context.clear();
     }
 
     // Xom thinks it's hilarious the way the player picks up an ever
diff --git a/crawl-ref/source/wiz-mon.cc b/crawl-ref/source/wiz-mon.cc
index eaccf8346e..7817b29e2d 100644
--- a/crawl-ref/source/wiz-mon.cc
+++ b/crawl-ref/source/wiz-mon.cc
@@ -23,6 +23,7 @@
 #include "monplace.h"
 #include "monspeak.h"
 #include "monstuff.h"
+#include "mon-iter.h"
 #include "mon-util.h"
 #include "output.h"
 #include "religion.h"
@@ -253,13 +254,9 @@ void debug_list_monsters()
     std::string prev_name = "";
     int         count     = 0;
 
-    for (int i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi; mi; ++mi)
     {
-        const monsters *m = &menv[mon_nums[i]];
-        if (!m->alive())
-            continue;
-
-        std::string name = m->name(DESC_PLAIN, true);
+        std::string name = mi->name(DESC_PLAIN, true);
 
         if (prev_name != name && count > 0)
         {
@@ -276,15 +273,15 @@ void debug_list_monsters()
         count++;
         prev_name = name;
 
-        int exp = exper_value(m);
+        int exp = exper_value(*mi);
         total_exp += exp;
 
-        if ((m->flags & (MF_WAS_NEUTRAL | MF_CREATED_FRIENDLY))
-            || m->has_ench(ENCH_ABJ))
+        if ((mi->flags & (MF_WAS_NEUTRAL | MF_CREATED_FRIENDLY))
+            || mi->has_ench(ENCH_ABJ))
         {
             continue;
         }
-        if (m->flags & MF_GOT_HALF_XP)
+        if (mi->flags & MF_GOT_HALF_XP)
             exp /= 2;
 
         total_adj_exp += exp;
@@ -338,9 +335,8 @@ void wizard_spawn_control()
     {
         // 50 spots are reserved for non-wandering monsters.
         int max_spawn = MAX_MONSTERS - 50;
-        for (int i = 0; i < MAX_MONSTERS; ++i)
-            if (menv[i].alive())
-                max_spawn--;
+        for (monster_iterator mi; mi; ++mi)
+            if (mi->alive())
 
         if (max_spawn <= 0)
         {
diff --git a/crawl-ref/source/xom.cc b/crawl-ref/source/xom.cc
index 91d006d747..34f8392ee6 100644
--- a/crawl-ref/source/xom.cc
+++ b/crawl-ref/source/xom.cc
@@ -26,6 +26,7 @@
 #include "message.h"
 #include "misc.h"
 #include "mon-behv.h"
+#include "mon-iter.h"
 #include "mon-util.h"
 #include "monplace.h"
 #include "monstuff.h"
@@ -1197,14 +1198,10 @@ static int _xom_do_potion(bool debug = false)
 static int _xom_confuse_monsters(int sever, bool debug = false)
 {
     bool rc = false;
-    monsters *monster;
-    for (unsigned i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi(&you.get_los()); mi; ++mi)
     {
-        monster = &menv[i];
-
-        if (monster->type == MONS_NO_MONSTER || !mons_near(monster)
-            || monster->wont_attack()
-            || !mons_class_is_confusable(monster->type)
+        if (mi->wont_attack()
+            || !mons_class_is_confusable(mi->type)
             || one_chance_in(20))
         {
             continue;
@@ -1213,14 +1210,14 @@ static int _xom_confuse_monsters(int sever, bool debug = false)
         if (debug)
             return (XOM_GOOD_CONFUSION);
 
-        if (monster->add_ench(mon_enchant(ENCH_CONFUSION, 0,
+        if (mi->add_ench(mon_enchant(ENCH_CONFUSION, 0,
                                           KC_FRIENDLY, random2(sever))))
         {
             // Only give this message once.
             if (!rc)
                 god_speaks(GOD_XOM, _get_xom_speech("confusion").c_str());
 
-            simple_monster_message(monster, " looks rather confused.");
+            simple_monster_message(*mi, " looks rather confused.");
             rc = true;
         }
     }
@@ -1541,24 +1538,16 @@ static int _xom_swap_weapons(bool debug = false)
     }
 
     std::vector<monsters *> mons_wpn;
-    for (unsigned i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi(&you); mi; ++mi)
     {
-        monsters* m = &menv[i];
-
-        if (!m->alive())
-            continue;
-
-        if (!you.see_cell(m->pos()))
-            continue;
-
-        if (!wpn || m->wont_attack() || m->is_summoned()
-            || mons_itemuse(m) < MONUSE_STARTING_EQUIPMENT
-            || (m->flags & MF_HARD_RESET))
+        if (!wpn || mi->wont_attack() || mi->is_summoned()
+            || mons_itemuse(*mi) < MONUSE_STARTING_EQUIPMENT
+            || (mi->flags & MF_HARD_RESET))
         {
             continue;
         }
 
-        const int mweap = m->inv[MSLOT_WEAPON];
+        const int mweap = mi->inv[MSLOT_WEAPON];
         if (mweap == NON_ITEM)
             continue;
 
@@ -1567,11 +1556,11 @@ static int _xom_swap_weapons(bool debug = false)
         // Let's be nice about this.
         if (weapon.base_type == OBJ_WEAPONS
             && !(weapon.flags & ISFLAG_SUMMONED)
-            && you.can_wield(weapon, true) && m->can_wield(*wpn, true)
+            && you.can_wield(weapon, true) && mi->can_wield(*wpn, true)
             && !get_weapon_brand(weapon) != SPWPN_DISTORTION
             && (!is_artefact(weapon) || _art_is_safe(weapon)))
         {
-            mons_wpn.push_back(m);
+            mons_wpn.push_back(*mi);
         }
     }
     if (mons_wpn.empty())
@@ -1677,18 +1666,9 @@ static int _xom_rearrange_pieces(int sever, bool debug = false)
         return (XOM_DID_NOTHING);
 
     std::vector<monsters *> mons;
-    for (unsigned i = 0; i < MAX_MONSTERS; ++i)
-    {
-        monsters* m = &menv[i];
-
-        if (!m->alive())
-            continue;
+    for (monster_iterator mi(&you); mi; ++mi)
+        mons.push_back(*mi);
 
-        if (!you.see_cell(m->pos()))
-            continue;
-
-        mons.push_back(m);
-    }
     if (mons.empty())
         return (XOM_DID_NOTHING);
 
@@ -1741,24 +1721,16 @@ static int _xom_rearrange_pieces(int sever, bool debug = false)
 static int _xom_animate_monster_weapon(int sever, bool debug = false)
 {
     std::vector<monsters *> mons_wpn;
-    for (unsigned i = 0; i < MAX_MONSTERS; ++i)
+    for (monster_iterator mi(&you); mi; ++mi)
     {
-        monsters* m = &menv[i];
-
-        if (!m->alive())
-            continue;
-
-        if (!you.see_cell(m->pos()))
-            continue;
-
-        if (m->wont_attack() || m->is_summoned()
-            || mons_itemuse(m) < MONUSE_STARTING_EQUIPMENT
-            || (m->flags & MF_HARD_RESET))
+        if (mi->wont_attack() || mi->is_summoned()
+            || mons_itemuse(*mi) < MONUSE_STARTING_EQUIPMENT
+            || (mi->flags & MF_HARD_RESET))
         {
             continue;
         }
 
-        const int mweap = m->inv[MSLOT_WEAPON];
+        const int mweap = mi->inv[MSLOT_WEAPON];
         if (mweap == NON_ITEM)
             continue;
 
@@ -1771,7 +1743,7 @@ static int _xom_animate_monster_weapon(int sever, bool debug = false)
             && !is_special_unrandom_artefact(weapon)
             && !get_weapon_brand(weapon) != SPWPN_DISTORTION)
         {
-            mons_wpn.push_back(m);
+            mons_wpn.push_back(*mi);
         }
     }
     if (mons_wpn.empty())
@@ -2846,22 +2818,18 @@ static int _xom_player_confusion_effect(int sever, bool debug = false)
         bool mons_too = false;
         if (coinflip())
         {
-            for (unsigned i = 0; i < MAX_MONSTERS; ++i)
+            for (monster_iterator mi(&you.get_los()); mi; ++mi)
             {
-                monsters* const monster = &menv[i];
-
-                if (!monster->alive()
-                    || !mons_near(monster)
-                    || !mons_class_is_confusable(monster->type)
+                if (!mons_class_is_confusable(mi->type)
                     || one_chance_in(20))
                 {
                     continue;
                 }
 
-                if (monster->add_ench(mon_enchant(ENCH_CONFUSION, 0,
+                if (mi->add_ench(mon_enchant(ENCH_CONFUSION, 0,
                                                   KC_FRIENDLY, random2(sever))))
                 {
-                    simple_monster_message(monster,
+                    simple_monster_message(*mi,
                                            " looks rather confused.");
                 }
                 mons_too = true;