Make draining temporary (for monsters)

The hit dice-reduction effect of draining has historically had
several problems. It reduced monsters' maximum hp, which made it
look like they were getting *less* injured, since they had a
higher proportion of hp remaining. It lowered monster XP & piety
gains, which was irrelevant but misled new players who somehow
learned about it. It occasionally led to "degenerate" hit-and-run
tactics.

And most damningly of all, it hardly ever mattered - it
triggered on ~13% of hits, which meant that on low HD monsters
the extra damage would kill them before the effect was
noticeable, and against high HD monsters, the effect would only
ever be noticeable at all with the aforementioned hit-and-run
tactics.

So, to fix those problems, draining now gives a "drained" status,
that reduces monster HD for most combat-related purposes
(spellcasting, accuracy, damage, etc.), but not max hp, xp, or
piety. This is temporary, but will last 20-30 turns, and
refreshes every time the drain triggers - essentially, it should
last until you kill the monster, unless you run away.

The temp-status is now applied to the monster every time they get
drained; the chance of the drain brand activating has been reduced
to 1/2, from 2/3. This should focus the effects of the brand more
on the unique part of it, the draining/weakening effect.

As a bonus, this also means that players can no longer have their
followers permanently weakened by draining effects. Beogh buff!

1 files changed, 10 insertions, 0 deletions

diff --git a/crawl-ref/source/mon-info.cc b/crawl-ref/source/mon-info.cc
index 052d3712e5..a37001ff8e 100644
--- a/crawl-ref/source/mon-info.cc
+++ b/crawl-ref/source/mon-info.cc
@@ -193,6 +193,12 @@ static monster_info_flags ench_to_mb(const monster& mons, enchant_type ench)
         return MB_SHROUD;
     case ENCH_CORROSION:
         return MB_CORROSION;
+    case ENCH_DRAINED:
+        {
+            const bool heavily_drained = mons.get_ench(ench).degree
+                                         >= mons.get_experience_level() / 2;
+            return heavily_drained ? MB_HEAVILY_DRAINED : MB_LIGHTLY_DRAINED;
+        }
     default:
         return NUM_MB_FLAGS;
     }
@@ -1604,6 +1610,10 @@ vector<string> monster_info::attributes() const
         v.push_back("ghostly");
     if (is(MB_SLOW_MOVEMENT))
         v.push_back("covering ground slowly");
+    if (is(MB_LIGHTLY_DRAINED))
+        v.push_back("lightly drained");
+    if (is(MB_HEAVILY_DRAINED))
+        v.push_back("heavily drained");
     return v;
 }