When I started playing Angband I was surprised of the mold type enemies. "A strange growth on the dungeon floor", if I remember the description correctly.
Lately I felt inspired to work on some studies about such "strange growth on the dungeon floor".
Dungeon Mold
(http://www.funkelwerk.de/data/study/unreality/molds/dungeon_mold_3_t.jpg)
Click to view full size.
(http://www.funkelwerk.de/data/study/unreality/molds/dungeon_mold_3.jpg)
Danger Mold
(http://www.funkelwerk.de/data/study/unreality/molds/danger_mold_t.jpg)
Click to view full size.
(http://www.funkelwerk.de/data/study/unreality/molds/danger_mold.jpg)
Rock Mold
(http://www.funkelwerk.de/data/study/unreality/molds/rock_mold_t.jpg)
Click to view full size.
(http://www.funkelwerk.de/data/study/unreality/molds/rock_mold.jpg)
The latter two are the same image, just with different color and contrast.