Quote Originally Posted by PId6 View Post
You can't improve a class's spellcasting beyond the normal limits pre-epic. This is true of every spellcasting PrC, from Assassin to Ur Priest. At best, if allowed, it would only increase your caster level, not spell slots. There's no progression beyond what's listed.
It doesn't matter how things are "supposed to" work, this is how DM is going to let things happen.