Sacred Haven of Debauchery

and rob caravans

You can't.

And I always play as Necromancers. And I always win. Well, sometimes I make a half-Necromancer, half-some-other-mage. But I can't do without Necromancy.

That's because you're a fanboy.
In D&D CRPGs, choosing a specific school doesn't affect the character's specialization; it simply prohibits one of the other schools.