Background
Motivation
Honor, - After a bad job from the empire, involving a change in the reward and threats to accept it otherwise, as well as an ever growing distaste for the empires treatment on non-human races, including himself and his own people, he sided with the rebellion and is current offering his command and combat experience for free, so long as he's fed and given the equipment and personel.
Although he never took part in large scale positions, he'd heard of the jobs the mepire offered, often outright cruel. Their treatment of civilians, even human civilians, on some worlds was also unforgivable. And, in regards to his culture, the way the empire treated their hunts with little honor goes against his very nature.