ToME: the Tales of Maj'Eyal

It appears that a necromancer gets rewarded with experience from his own will'o wisps when they explode.

So.. Theoretically, you could level up to level 50 in Derth? Summons, and Wisps both level with the player, right?

I wonder what happens if you trigger the Storming the City quest while you are standing in Derth.

Well, I don't think they give much exp - it'd be stunningly boring.