War TARDIS

91-form timeships, also called "War TARDISes" and "Ships of War", were created by the Time Lords in the years immediately before the War.

Characteristics
War TARDISes were reared/born/controlled via a Bull-TARDIS in the time vortex. (PROSE: The Taking of Planet 5) Though not recognisably intelligent, the minimum-intensity biodata in their structures gave them a biological edge, suggesting they were aware of life on their pilots' level. (PROSE: The Book of the War)

They could map their interior dimensions onto the outer dimensions, making for an imposing sight. (PROSE: The Ancestor Cell) In fact, 91-forms were the first timeships intentionally designed to be indiscreet, appearing as consistently big, bulky, and unapologetic. In orbit, they were often mistaken for arks or flagships of lesser species; however, they more often rooted themselves on planets at ground level, pushing aside buildings and taking the forms of giant cathedral-like embassies for the Great Houses. Some such grounded 91-forms were incapacitated or abandoned and dug out of the group millions of years in the localised future, misidentified by the natives as relics of a lost civilisation or the bones of huge, semi-mechanical monsters. (PROSE: The Book of the War)

They could not withstand many shots of weapons fire from the first Type-102 TARDIS known as Compassion. (PROSE: The Ancestor Cell)

Older versions, built during the Dark Times when the Time Lords fought the Great Vampires, were the size of comets and had unstable real world interfaces. One was damaged in the War and became known as the astronomical body Cassandra. (PROSE: So Vile a Sin)

Uses
"Military TARDISes" were sent to collect the Sixth Doctor from Etarho in a displaced timeline. (AUDIO: Trial of the Valeyard)

House Mirraflex used 91-form variations in their assault on the City of the Saved. (PROSE: Timeships)

When the Master came under attack by the Divine Host of the Chronovores, the Quantum Archangel altered reality and changed his TARDIS into a "Type 94" WarTARDIS, armed with Klypstrømic warheads, an artron cannon, a vortex lance, and Earthshock bombs. (PROSE: The Quantum Archangel)