You were raised on Mindoir on the fringes of the Attican Traverse. When you were sixteen, the colony was raided by slavers. The entire settlement was razed and your friends and family were slaughtered. A passing Alliance patrol rescued you, but all you loved was destroyed.
You enlisted with the Alliance military, eventually volunteering to go to Akuze, a colony that had mysteriously dropped out of contact. As soon as it arrived on the surface, your patrol was attacked by thresher maws - mindless abominations of teeth and tentacles that rose up from beneath the earth. Constant gunfire couldn't drown out the shrieks of your fellow soldiers as they were dragged down to a gruesome death.
Fifty marines died on Akuze; you were the only one to make it back to the landing zone alive. A monument on the planet commemorates the massacre, a grim reminder of the price humanity must pay as they spread throughout the stars.