ToME: the Tales of Maj'Eyal

Unnatural Body never seems to heal me for any amount. I kill things and my hp and hp regeneration rate stay as they were.

If you mean the HP regen thing over your health bar, that stays the same. But every time you kill something, if you look closely at your character and move, you'll see a bunch of little yellow numbers springing out of your character. Those are the heals.

I didn't get it at first, either