Captain Sarah Parks was a combat surgeon on Protasia when the planet errupted in full scale rebellion against the Emperor and began slaughtering the human symbols of his authority.  One of the few survivors who escaped the capitol city, she managed to dump a highly poisonous compound into their water supply before being extracted.  Her actions killed thousands and sickened thousands more before the rebels discovered the problem.  She has since been seconded to the Inquisition on request for an "extended detached duty" assignment.

Currently, along with Sister Mercia, she is the Medicae Officer aboard the Renegade.