Necropolis and Demon.

After the first few turns, the demons will have decimated the Necromancer's initial forces, leaving very few troops remaining:smile42:. And he won't have enough mana to summon more. So, what's the point of spiritual connection? By the time they arrive, a hundred years will have passed, and meanwhile, the demons will have already wiped out all the skeletons and started attacking the remaining troops (and they can do it simultaneously).