Stor

Stor was a Commander in the Sontaran Special Space Service and the leader of the forward task force in the attempted Sontaran invasion of Gallifrey. He was identified from the other soldiers in his unit by a large rim on his helmet along with a bold white crown logo above the enlarged eye holes. The logo was similar to (if not the same as) the one on Linx's helmet where it was made out of dots. He also did not wear gauntlets, unlike the rest of his troops. Stor was equipped with a side-arm, communications equipment, and at least one grenade.

His mission was to seize and hold the Capitol and open the transduction barrier further so that the rest of the invasion force could land. Stor was killed when the the Fourth Doctor activated the forbidden Gallifreyan De-mat Gun which took Stor and his unit out of time and space. It also wiped the Doctor's memory of the events of the Sontaran and Vardan Invasion. (TV: The Invasion of Time)

Stor was among the foes who the Fourth Doctor saw call out to him in his mind shortly before his fall from the Pharos Project radio telescope, which resulted in his regeneration to his next incarnation. (TV: Logopolis)

Behind the scenes

 * Commander Stor and his battle on Gallifrey is mentioned by Commander Strax in the fourth-wall-breaking cinema intro for The Day of the Doctor. He is disappointed to learn that the anniversary feature is about the Doctor as opposed to a Sontaran historical drama featuring heroic accounts of their various military campaigns which he was anticipating with his clone batch.