Play against Necropolis.

By the way, regarding having no positive spirit units. This can also be fixed. Orc leadership always increases, meaning it will always be 5. It's not that difficult to find an artifact that increases spirit, even if only by a small amount, but it does increase it, plus a couple of buildings before the final battle, and your army is almost completely saved from the Necromancer's super ability. The only thing is, the final battle might come unexpectedly, but it's unlikely; I think the Orc will go to the Necromancer because the Orc shouldn't waste time. BUT, it's true that it's better not to wait for the Necromancer to upgrade his special ability; I agree with Crol.