I don't think dragon souls are freed when the dragonborn dies cause then at best they would only be delayed from resurrecting for a few years you get the felling from the main quest that absorbing a dragons soul is kind of permanent.

Perhaps you can side with him and rule over the island as his second in command of sorts like a Vader, Palpatine situation?

hopefully a shorter cooldown for shouts will be earned when we slay him, or it could be that his soul belongs to herma-mora and is reclaimed by the daedra upon death

Certainly a good idea, specially if it isn't bugged like Call of Valor with conjuration.

What would svck is if you killed him and a nearby dragon stole all of the souls, because the dragons themselves can devour souls of their fallen brothers.
Then that dragon turned on you with the knowledge and power of the first dragonborn and who knows how many dragons.

I think what will happen is that after you kill the Original Dragonborn he will have the same death animation as Alduin

That might kill him.


He would most likely turn out to be another lord Harkon.

This realm is to small for two, cowboy.

Dragonborn: How are the Kids?
Ancient Dragonborn: The Kids are fine, the Oblivion Realms does wonders to thier fears.