Vicious Gaan-Telet as a vampire. Got an Animated Armour down to 1HP with no death protection and a layer of burning. Left the floor, killed a lvl1 Meat Man, got experience for the AA. Went back. The AA is still there with 0HP, invisible, immortal and fighting back. Tried attacking it normally and with fireball, no effect. On the screenshot, the AA is standing one tile below me.
ScreenshotYet another reason to remove this floor, if you ask me