Never said anything about Hazoret. She isn't mentioned on said picture, either, for this very reason.
Elspeth is the most common guess, although it's hard to say how her going to the underworld turned her into a Katana-wielding "Pssh, nothing personal, kid" swordswoman. I have my doubts about that. Some people think it's an avatar of Emrakul based on her depiction on
Shrine of the Forsaken Gods, but that seems pretty silly, too.
My guess it's a new, unrelated character that acts as a plot hook for the future.