It's exactly what it sounds like: he's from an action game canon ala Bastion, but Turn() is a power of the Transistor. It essentially lets you plan out a series of actions and instantly execute them, with a cooldown.

In AU, I'd have to give him a name and history. And his OU gives you enough of his history to understand his background, if you pay attention: He's a grifter that exists outside of the system, having mostly remained an observer who participated in things outside of the city's scope until he met Red.

He doesn't need a defined face - it'll be handwaved, since I don't really need to talk about his face or anything. But he probably would be just as secretive with his real name as he was in the game proper. I don't know if he's actually called Boxer or not, even: that's actually a name pulled from the game's code itself!

In-code, Red is referred to as Muse, and Boxer (or "Blue" as people like to call him) is called, well, Boxer.

Transistor is a wonderful game with excellent worldbuilding and a deliberately minimalist narrative. I'm hoping we see it get some kind of fleshing out - even a novel would be wonderful.