What skills should Necromancers take when facing Orcs on a very large map?

What if you develop the Necropolis? Light. All mass spells. Education. Logistics. Luck. And the rest, as you choose:) Machines, Darkness for vampirism, or something else.

But the Necromancer won't even have time to walk around for 3-4 turns, what can be done in that time? Light won't help much, nor will luck! The only way is to overwhelm with numbers and subjugation, which is quite difficult because goblins block it effectively. I think the best approach is to fight to the last, focusing on education, wizardry, and darkness.