I'm me. Who else could I be?
Darth Oblivion, or Lord Oblivion as he was called by lesser beings out of feigned respect, was a Sith Lord who did stuff. Nobody knew who he was or could remember who he was, hence the "Oblivion." Anyone who met him would entirely forget the encounter soon after. Even the dark lord himself wasn't too sure who he was, or what...it was. Wait... How do we know he was even male? Why are we referring to him, err...it as a "he"? It could have been a woman or a damn hermaphrodite for all we know. Well, we know this entity was indeed a most powerful Sith Lord...or do we? Blarg! Ok, Darth Oblivion was a being who may have also been called Lord Oblivion, may have been a powerful Sith Lord, and may have done stuff.