Type 91

A Type 91 TARDIS was a type of War TARDIS alongside Type 94s. They were created by the Time Lords to fight the Great Vampires in the Eternal War. (PROSE: The Brakespeare Voyage, Doctor Who and the Krikkitmen)

They were intentionally designed to stand out and appear big and bulky. They would sometimes become stuck on planets and become embassies for the Great Houses. (PROSE: The Book of the War)