Bull-TARDIS

Bull-TARDISes, or bull-engines, were a type of TARDIS.

War TARDISes were controlled through a Bull-TARDIS in the time vortex. (PROSE: The Taking of Planet 5)

Romana III wished to mate a Bull-TARDIS with Compassion to create the first Type 103 TARDISes; (PROSE: The Shadows of Avalon) later, 103-forms were bred through the mating of older 103-engines with bull-engines. (PROSE: The Book of the War)