Dragon Ball Xenoverse
We recently learned Xenoverse's mysterious character is a player-customized avatar. Now we know why they're fighting alongside Goku and pals.
In the game's TGS trailer, we learn that the Dragon Ball Z timeline is askew. Things are out of whack, and to help restore balance, Shenron (the dragon summoned by collecting the Dragon Balls) has brought the fellow you see on the right above. A character that can be customized to the player's liking.
The trailer also reveals that the game is planned for release on PC via steam, alongside Xbox One and PlayStation 4, and Xbox 360 and PlayStation 3.