Thread:Mesektet/@comment-26083398-20151118224325/@comment-26083398-20151119154025

That's what I thought too at first, although I found that in Skyrim, he requests the Dragonborn in to eliminate a traitor who dishonored him, he states that if they defeat the enemy, he shall cleanse the disease the Afflicted carry from the surface of Nirn (or something like that).

It's mentioned that he is considered to be one of the weaker Deadric Princes (despite being depicted as a Dragon), it could be that in the fifth installment (which btw is set like 200 years after the first 4), he has a more empathic change of heart for mortals as evidence by the aforementioned quests, and that he is attempting to help the mortals by now cleanseing diseases in in an act of vengenace and defilince against the Deadra (particularly the ones that are considered evil).