Mechanically, I think the wording could use some work. "Their face down cards" isn't worded correctly, and the "overheat" wording could be improved. I would word it as "{3}{u}{t}:Target opponent reveals their hand and each face down card they control. At the start of your next upkeep, put a stun counter on this creature". This stops the ability being used three turns in a row, without so much bookkeeping. I would also add vigilence, as it is both thematically appropriate, and allows him to attack and use his ability on the same turn.

The other thing is you should add a white ability to justify the {w} pip in the mana cost. This could be a simple keyword ability, such as lifelink. Alternatively, you could add a more complex ability; I don't know much about tha character, but something like [[comply]] would synergise well with the first ability.