I've played the game through (no mods, just KOTN and SI) 3 or 4 times. On my last play through I found Lost Boys Cavern(?) for the first time, which gave some of the backstory for the necromancers. I think it would have been better if that had been included in the Guild Mage questline.
Anyway, I was wondering if there is anything similar for all those conjurers running around. Why are they trying to find the Shield of the Crusader? Why the dead captives in another cave? Why do they infest so many Ayleid ruins? Why are they so closely allied with Daedra?