Highspire Experimental Castoff (Rager)

A product of the theoretically illegal practice of modifying the human body with alchemy, magic and/or robotics, you either escaped your creator or were somehow cast aside after serving your purpose.
A castoff Rager doesn't merely lose their temper when they rage, they lose a certain amount of control of their physical form. Shifting to appear more like the monstrous creature they were designed to be grants them access to great power, but costs them a certain amount of self-control and risks alienating those who realize that the Rager is anything but normal.
Perhaps this is rage is inspired by your condition, perhaps it is supernatural, perhaps a natural reaction to your circumstances. That rage makes you incredibly dangerous for foes, and in some circumstances, your friends as well.