Miz: The desire to end slavery. First of her own people, then that of others. On an extremely close second is the desire for vengeance. To burn the Empire down around the 'faithful' who allowed this to happen in the first place. Why? Well... a former slave herself, she's seen the result of indoctrination and oppression first-hand, along with the erasing of a cultural identity she can feel in her blood but not truly know after the upbringing. She knows the horrors of the Empire and thus is compelled to end it, by any means necessary.
Katashi: Finding a purpose. He doesn't really have one, and it's eating away at him. He makes jokes about Electronic Engineers being 'his people' and that his place and purpose in the world is to be the cigar smoking crooked smile wearing fellow who gets the nutshots and girders to the back of the head. And perpetually blueballed, for that matter. But beneath the surface, there's a hunger for purpose and a position in the world.
I've got a few others, but they're not really someone I've put a deep drive behind.