I guess this is a completely hard question considering there is very very little information. I would guess that is someone related to Xehanort considering his dark Keyblade, which has features similar to the other Foretellers. I would go as far to assume his the player that went to darkness to which the dark chirity refereed to. Maybe he wasn't dark until that very moment, and its because of Xehanort going to the past and changing stuff in order to try to advance the process of him becoming part of the darkness.
Ansem seeker of darkness in KH1 said some peculiar words that didn't make since until now: You have come so far and yet you do not know nothing, you understand nothing. Peculiar phrase for an old guy, who simply manage to control a heartless and a Nobody of himself which in turn is from the body of someone else (Terra's body).
That's all I can think of... xD