"With this character's death, the thread of prophecy is severed. Restore a saved game to restore the weave of fate, or persist in the doomed world you have created."
You can also use him for the quests THEN kill him. Personally I think that plotline is mostly funny in the pure absurdity of his character, but like many things in that game (crassius curio anyone?) he's pretty damn sketchy to say the very least. Personally my fave councilor out of all three houses is Aryon, who is significantly less sketchy.
Oh it's for sure meant to be a little humorous in its absurdity, but once I found out about the daughter-wife clones, I made a myself a lil quick save for prophecy reasons and then set about exploring an alternate timeline lol.