Alistair

[PLEASE NOTE: I am not currently well-versed in the workings of dissociative identity disorders, and hope that my ignorance does not come across as malicious.]

Due to being tortured and abused relentlessly as a child, Alistair subconsciously developed a split personality in order to better deal with his situation. His original personality is kind, loyal, gentle and caring, having blocked out all of his tortured memories, while his alternate persona is the exact opposite. He's a monster that enjoys pain and torture (both inflicted on him and on others) and is very much a sado-masochist and is very cruel. This personality usually "wins out" majority of the time due to his mind having been broken down so much, but sometimes can be found taking a stroll through an empty field with a kind, carefree smile. He used to live in a desert mountainside with a large heard of fellow bison, and would offer help to his neighbours often, but he learned that they feared him due to his alternate personality, and fled to live a life on the outskirts, in an attempt to keep the community safe from him. His original captors tracked him down after a brief period of time, entering into an encounter that eventually ended with their bloody deaths and gruesome dismemberment. Now he lives on the outskirts of a large city where no one knows of him, and the only clues to his whereabouts are the whispers in dark alleys on cold, moonless nights.

Although he is pansexual, Alistair generally takes a preference for female sexual partners, but will still play with a male if one takes his fancy.
His original personality is quite submissive and versatile, while his alternate personality is VERY dominant, oftentimes not even waiting for his partner's consent, or playing mind games with them if they do.

It is still unknown as to what trigger, if any, initiates his switch in personalities.

His mechanical arm is usually made up of scrap parts that he finds scattered around, usually in rubbish dumps and recycling bins. It is often destroyed in his alternate self's activities, leaving his original self to constantly mend and reconnect it.