Gosolus

Gosolus was one of a number of worlds that had launched attacks on Gallifrey in the time that passed between the Triumvirate and the Infinity Doctor. Gallifrey won the conflict and celebrated its victory in the Capitol with a victory parade which was retraced monthly by a ceremonial march. (PROSE: The Infinity Doctors)

Behind the scenes
Gosolus originated in the Audio Visuals series of unofficial Doctor Who audios. Adrian Middleton's treatment of Gosolus in his Apocrypha influenced the mention of the planet in The Infinity Doctors.