Ghost crabs (PleasingFungus, floatingatoll).

They have stats similar to fire crabs but slightly stronger. Instead
of fire clouds, they breathe clouds of ghostly flame, the spell that
revenants have.

I think that they combine two fairly unused monster mechanics -- the
"big cloud" that crabs have and the otherwise-unused ghostly flame --
to create a monster that is fairly understandable based on previous
ones but has interesting gameplay. Unlike revenants, they are not
spellcasters, and the cloud is more about bringing fellow monsters
to beat you up, since it does less damage, their HD being lower. They
also contribute a few more non-undead to Crypt, which I think is good
to have.

I'm not certain about the spawn weight, but in tests they seemed to show
up once or twice a level on Crypt:1 which seems about right. They simply
replace mummies in Tar; this doesn't seem very controversial.

1 files changed, 1 insertions, 1 deletions

diff --git a/crawl-ref/source/tilepick.cc b/crawl-ref/source/tilepick.cc
index 844f25ef31..8b8ccdee4a 100644
--- a/crawl-ref/source/tilepick.cc
+++ b/crawl-ref/source/tilepick.cc
@@ -912,7 +912,7 @@ static tileidx_t _tileidx_monster_zombified(const monster_info& mon)
     case MON_SHAPE_QUADRUPED_TAILLESS:
         if (mons_base_char(subtype) == 'F')
             z_tile = TILEP_MONS_ZOMBIE_TOAD;
-        else if (subtype == MONS_FIRE_CRAB || subtype == MONS_APOCALYPSE_CRAB)
+        else if (mons_genus(subtype) == MONS_CRAB)
             z_tile = TILEP_MONS_ZOMBIE_CRAB;
         else if (subtype == MONS_SNAPPING_TURTLE || subtype == MONS_ALLIGATOR_SNAPPING_TURTLE)
             z_tile = TILEP_MONS_ZOMBIE_TURTLE;