I've rarely used undead, but am about to dump them on my PCs in quantity. Reading the Create Undead spells, it says the duration is Permanent and that they can be "Dispelled, Repelled, or just smashed into little pieces."
I don't have it handy right now, but if I recall, in Creatures and Treasures, undead that go below 0 HP drop, but they will regenerate with time and later be able to fight again. Is there some exception that says cleric-created undead are truly dead at 0 HP, or will they, too, regenerate slowly?
I've got a necromancer in the woods who animates animal corpses, and I'm wondering if, over time, they'd just be building up and building up, regenerating after they get knocked to 0.