What with the talk of Bleach earlier, I'm surprised no one mentioned Aaroniero Arruruerie....
He's one of the recently appearing humanoid "Arrancar" hollows, who get stronger by tearing their masks off and becoming more similar to their Soul Reaper enemies (i.e they get swords and stuff).
That's what he looks like behind his mask. Though at the beginning of his screen time he's disguised as a long-dead Soul Reaper, a victim of another, parasitic Hollow that Aaroniero had previously consumed to gain its abilities.
Aaroniero's "sword", Glotonería, manifests as an extra mouth/arm in its power-condensed form.
When he releases the sword's power, he takes on this form. The person at the top is the puppeted body of the aforementioned dead Soul Reaper