Pax wrote:
Undead always gain d12 Hitdice. Even for classes. Look to the Lich as an example.
But the question was specifically about adding class levels to
non-templated undead. I don’t believe that Savage Species directly addresses this question, but even when the book addresses adding class levels to undead templates, SS is irreconcilably contradictory.
In Savage Species, the most definitive statement occurs on page 17, in the sidebar "Templates and Classes": "Once a creature becomes undead, all its Hit Dice become d12s. Any dice gained afterward from class levels are also d12s, regardless of class." One might infer that this statement holds for all undead, templated or not.
And Table 10-1: Hit Dice and Templates shows that all of the undead templates complete change a monster’s previously acquired HD and continue to change future HD gained with class levels. Again, this suggests using all d12s.
But once you start getting into the descriptions of the undead templates in Chapter 10, you start finding comments like this under "Spectral Characters," page 131, "Spectral characters with class levels generally take levels of barbarian, fighter, or ranger. These classes offer good Hit Dice . . ." A similar statement is made about wraith characters – suggesting that undead with class levels may not use all d12s.
So if Savage Species doesn't clearly answer the original question, we can turn to the next published authority, the 3.5 Monster Manual. The 3.5 MM introduces much better language in the "Size and Type" line of the template description that clearly indicates all 3.5 undead templates change "all current and future Hit Dice to d12s."
So where does that leave us with non-templated monsters? The 3.5 MM does not explicitly state that all undead HD, templated or not, should use d12s. Further, the mummy lord entry clearly separates out mummy HD (d12s) from cleric HD (d8s). So, I’m inclined to think that unless the monster description specifically says otherwise, class levels added to a non-templated undead should use regular class HD.