Archer

Archer was once an angel, a seraphim whose duty was to guide spirits to the afterlife.  However a deep rage stirred within; over time he became bitter, frustrated that those he led to the Heavens didn't always go where he felt they should.  He held great resentment against his God, which eventually led to his downfall.  He tried to fight back, and was thus cast from heaven.  His wings were bound to stop him from flying back, his leg severed as punishment for his rebellion.  Furthermore, he was cursed to turn into a monster whenever he became angry from that point on.

Lost and alone in this unfamiliar world, Archer largely keeps to himself.  Occasionally he is visited by other canines or Max - the archangel tasked with watching his movements - but he doesn't seek out company.  He's very closed off and finds connecting with others difficult.  In his eyes, people are not worth trusting and he doesn't want to be hurt again.