Who he is: The Mandarin. (The real one.)
His power: Unknown. In the comics, The Mandarin possesses 10 alien rings that give him a variety of powers; in the Marvel Cinematic Universe, though, all that’s known is that he’s brilliant, vengeful, and in charge of a massive terrorist organization.
His story: The Mandarin’s existence is first hinted at, but never mentioned, in Iron Man, when playboy weapons manufacturer Tony Stark is kidnapped by his terrorist organization, the Ten Rings. The Ten Rings also pop up in Iron Man 2, helping to smuggle Whiplash into Monaco, and Ant-Man, where one of its agents attempted to kill Hank Pym. In Iron Man 3, though, Aldrich Killian hires a British actor named Trevor Slattery to impersonate The Mandarin in order to manipulate the War On Terror, an act that would later have disastrous consequences for Slattery. Although it was believed, at the time, that The Mandarin was simply an invention of Killian’s, the short film All Hail The King reveals that he is very much real. His agent, Jackson Norriss, abducts Slattery from prison, saying that The Mandarin is angry with him for the impersonation.
Played by: Nobody, yet.
Currently, The Mandarin is: Using Ben Kingsley as a punching bag, is our best guess.
Where will we see him next? Technically, we haven’t even seen him. And since Iron Man 4 isn’t on the books yet, your guess is as good as ours for when The Mandarin will make the leap from one-shot Easter egg to onscreen evil.