So one of my players want to make a Dread Necromancer

[Dausuul]

i agree with kasrkin.

Is there actually a class called Dread Necromancer? What book?

Heroes of Horror. The dread necromancer is to necromancy what the warmage is to evocation, and the beguiler is to enchantment/illusion.

I'd say nothing but regular human corpses, and don't give him too many of those--maybe 8, tops. If he's willing, I would also suggest dividing up the army among the other players so they can all control some; that way the dread necro isn't taking up 80% of the combat time.