Daedric Servant Theory:
Many have wondered, how is it that you sumon daedra? What do they get in return for it? My theory is that they get to keep the souls of those they kill, and they use those in my later theory.
Perhaps the souls that are captured are used to be transformed from human to daedra, making new daedra, basically the atronach forge turning human heart to daedra heart, but backwards and with souls.
If daedric weapons and armor require hearts to make them, how do they have armor and weapons? Are they taken from slane humans and made into daedra hearts? Possibly, however I think its more likely they have some sort of Heart Cattle, as in lesser daedra that come back to life very quickly.
As all of you (Hopefully) know magicka respawns, many have questioned, how do they respawn? I think magicka is a gift from Magnus, who made the sun by punching a huge hole in tamriel, He gives you a infinite replenishing supply, like a Dwemer Centurion Dynamo Core, but only gives power slowly?