Q150: Is there any way to take levels in your type's racial HD? I mean, e.g. if you are a necropolitan wizard 1 and you advance in level, to take the new level in undead and be wizard 1/undead 1.
Not normally. Maybe by stealing the ability of a sharn or barghest or something.
I know this thread is "dead" but I was getting caught up and know an answer to this one.
Beast of Xvim template, Monsters of Faerun. It can be added to anything, and it has a Feed ability that gives it bonus (presumably racial) HD.