Screeling

A screeling is an undead creature. They are squat, hunched over creatures armed with long, wicked claws instead of fingers on each hand. Its eyes are black with a golden glitter

Screelings have a supernatural speed and strength, and can scale sheer surfaces and ceilings. The screeling laughs incessantly, even if being hacked to pieces. Screelings are unaffected by most magical attacks; setting one on fire only makes it more deadly. Weapons of any sort will damage its body, though axes are most effective.

A screeling's weakness is its vision. It only attacks people when they are standing still or are moving quickly. Anything moving at a slow, constant speed is ignored by the screeling (at least at first), causing its laughter to halt momentarily as it becomes confused. Screelings learn quickly to rely on other senses, and will eventually learn to recognize the walking people as targets.