By going into this subject I realize that the Ebony Warrior was just made to challenge the high level class characters.
I don't know why at level 81, you get this fool who's motive is to fight you to the death. His motive is lame. He claims he's beaten everything in his path which is way wrong. He could have used his skills and magic to make a difference in Tamriel but it probably would be a conflict of interests for the Ebony Warrior seeing as his goals are self serving. My guess was that he wanted to gain a load of power and than take it with him to Sovngarde.
But seeing as he doesn't show up in the main quest at the end. He must not have been worthy enough to go to Sovngarde. Some where down the road he must have already sold his soul either to a Daedric Prince to get more power or he did something to convince Shor that he didn't belong there.
Furthermore. I think his character could have better served Tamriel by taking out some more bad people. He seemed like a great guy. But the more I've looked into the character. He just seemed very suicidal and misguided by his beliefs. That being Religion. His beliefs were right up there with the code of Malacath.
I wonder what the Ebony Warrior might have done if he had killed The Dragonborn. But than again. The Ebony Warrior is shrouded in mystery.