Light for the Necromancer.

Well, in my opinion, summoning with high spell power is not that irrelevant in the late game, because raising the dead will be one of the most useful spells at the end of the battle! You can play as Vlad, and he will raise a lot of troops. In general, in the late game, it's unlikely that anyone will switch from Darkness to Light, and therefore you have to switch to summoning.