The Mummy in Horestis tomb, I forget it's name at the moment. Their corpse becomes unopenable within 10 seconds of killing. And most of the monsters in that tomb don't have their respectable bodies, they have the fiery blob of hellfire fighters and others such like. Also Dark torturers can't be opened by anyone but the killer. Not sure for how long but when someone killed one for me, I tried to open it 2 minutes later and it told me I wasn't the owner.