Q: Dear Sage,
Does an undead that takes class levels (i.e., a ghoul with fighter levels) use the class hit die for the class levels or a d12?
A: Vampires, liches, and other undead templates typically state that all HD are replaced with d12s; if the template doesn’t say so, assume the HD remains the same.
Normally, non-templated undead can’t have class levels—any exception is a very special case created for a particular purpose by the DM or adventure author. In such cases, the undead should probably use the normal class hit die, since the rules don’t say anything about changing it in such cases.
About the Author
The Sage is a mammal classified in the bear family, Ursidae, native to central and southern China. Debate continues as to whether he is truly a bear or more related to the raccoon rather than the bear, or perhaps in a family of his own. When not eating bamboo and answering rules questions, he works under the nom de plume of Andy Collins as an RPG developer in Wizards of the Coast R&D, where his development credits include Complete Mage, Dragon Magic, and the Player's Handbook v.3.5. He can be easily recognized by his large, distinctive black patches around the eyes, ears and on his rotund body.