Strax

Commander Strax was a Sontaran commander who was demoted to nurse as punishment for an unspecified failure. He fought and died at the Battle of Demons Run.

Biography
He was one of many people who owed the Doctor a debt. In the year 4037, he was tending to human soldiers at the Battle of Zaruthstra when he was summoned by the Doctor to help in the mission to rescue Amy and her baby at Demon's Run, which offered him a chance to once again experience the pleasure of battle. He was mortally wounded in the battle with the Headless monks when one damaged his probic vent. In his final moments, Strax noted how he had once longed to die in combat (which was common among Sontarans), and now, he didn't find it as enjoyable as he thought it would. Rory tried to comfort him, saying he was sure he would recover, but Strax wasn't fooled, reminding Rory that he was a nurse, too. However, he admitted that he had had a good life, and was pleased to live nearly twelve years. (DW: A Good Man Goes to War)