There is no cow level!
This is a cow -- or, possibly, a bull or steer, but usually a cow -- standing upright on its hind hooves. In its forehooves its wields an incredibly sharp poleaxe. Often the second warning of Hell Bovines is the glint of a target's lantern light off the poleaxe and the pointy ends of the horns. The first warning is when, out of the pitch darkness, one hears the angry baritone "Mooooooooo!"
Thanks to Joshua Goodreau who converted the Hell Bovines back in January 2014.