Partheus was assigned by the High Council to use the Tear of Isha to seal the Tantalus Eye to cut off the energy source of the Daleks' de-mat weapon which they planned to use to wipe Gallifrey from history.
En route, the radiation from the anomaly affected the flight systems of the TARDIS fleet, making it hard to navigate in the Time Vortex, so they had to travel in real space. The TARDISes were attacked by Dalek ships.
During the battle, the War Doctor landed his own TARDIS in Partheus' own ship, risking a time ram which would have destroyed them all. After a brief struggle, the Tear was deployed and it collapsed a star instead of the anomaly. Partheus then ordered the Doctor and Cinder off of his ship.
Cinder noticed the interior of Partheus' TARDIS was much larger than the Doctor's own TARDIS, by three or four times. There were three squat, hexagonal consoles rather than just one console, which were dark grey in colour. Cinder found their controls boring since unlike the Doctor's TARDIS they were smooth and manufactured in design rather than makeshift ones like on the Doctor's console.