Preda's Battle TARDIS (Engines of War)

Captain Preda of the Fifth Time Lord Battle Fleet commanded a Battle TARDIS which was the flagship of a squadron of a hundred or more similar Battle TARDISes. The Battle TARDISes were shaped like plain white lozenges with an outer skin of living metal, maybe Validium, which could morph into shields or weapons.

With the War Doctor, Preda intercepted a number of Dalek saucers in orbit of Moldox, close to the Tantalus Eye. The Battle TARDISes managed to destroy the Daleks, but they were destroyed by a squadron of Dalek stealth ships that appeared just after Preda and her fleet destroyed the saucers. The Time Lords led by Preda didn't have time to react before the Dalek stealth ships destroyed them.

Later Rassilon said to the War Doctor and Cinder when they arrived on Gallifrey that he'd watched Preda's death with a heavy heart, but Cinder felt he wasn't concerned. (PROSE: Engines of War)