Two ideas, just running by in general:

1) Alien species, Orsim is working name. Humanoid(and possibly/probably human divergent) and large.  Their evolution follows a "hard to break" rather than "easy to fix" pattern, somewhat opposite humans.  Tough skin and strong, but flexible bones, but they heal slowly and badly.  

2) Space vikings!  I've been working on a write up post for them in general, but it's been slow going for some reason.  But the idea is they live at the edge of the galaxy, their system is orbiting like everything else and every [arbitrary span of time] they have a different system that is in range for them to raid.  Their MO is land -> raid -> take off before Imperial reinforcements.  Their home system is full of like, black holes or asteroid fields or something that makes it difficult for strangers to navigate, making it a safe refuge for a space fairing folk.