- You may be looking for the ship in The Scarlet Empress.
Nearly three centuries into the War, when the surviving Faction had devolved into a militaristic sect of terrorists, (PROSE: The Gallifrey Chronicles) Kristeva and Mother Mathara led an invasion of Romana III's Gallifrey from the Eleven-Day Empire, (PROSE: The Ancestor Cell) sometime before its destruction early in the War's sixth decade, (AUDIO: The Shadow Play) to launch their own front against the enemy. (PROSE: The Gallifrey Chronicles) Mother Tarra was their agent, infiltrating the superstitious youths of Gallifrey driven towards Faction rites by the corrupting influence of the Edifice. (PROSE: The Ancestor Cell)
Travelling back in time to before the Event, (PROSE: The Gallifrey Chronicles) Kristeva manipulated the Eighth Doctor while Mother Mathara's warfleet waited for the invasion. The Faction took advantage of the Edifice's negative affect on Gallifrey's history and culture. Eventually, Kristeva and Mathara infected the Matrix, merging Gallifrey with the Eleven-Day Empire, solidifying their version of Grandfather Paradox, and destroying Gallifrey's eight cloneworlds.
The Doctor obliterated Romana's Gallifrey in an attempt to avert the War, destroying the possible Grandfather Paradox and Mathara's fleet. Kristeva and his Shadow Parliament were destroyed by this, the shock of the event causing them to combust or be attacked by darkened, shadowy birds before the planet exploded. (PROSE: The Ancestor Cell)