You can get a cleric as base class, then work into the Chameleon PrC. Get two levels of it for the floating feat, and choose the death domain in your base cleric, and choose the apropriate feats (the floating feat can't be used for requisites, I think).
Then you get into true necromancer with a single class, capable of casting arcane and divine and not hard to enter (you may want silverbrow human to get disguise as a class skill, tough). I would even distribute my true necromancer caster levels 5 to chameleon and 5 to cleric, and then get another 5 levels of chameleon for double aptitude.
Or if you fancy more an arcanist, you can have the sorcerer with the domain sorcerer variant, and choose the death domain. Might not be as great, but it is a possibility, and his class skills make it easier to qualify for chameleon. Knowledge (religion) might be a problem, tough.