The TARDIS is a time and space machine Vahl owns. Jordan used the TARDIS primarily to travel, but also used it to cheat the game and get inside 'The College Of Winterhold'.
The TARDIS has multiple Console rooms, but Vahl prefers the original.
It can travel to Standing Stones, Words of Power, Hold Capitals, and a custom location, which originally was outside Vahl's home on Solstheim, but was moved outside Fort Dawnguard. It was finally moved to outside Vahl's current house in Windhelm.
It was originally owned by Jordan's old character, Trinity, though, either by design or chance, was sent into Vahl's timeline and came into her possession.
It has had many companions, Vahl's companions being most, but has also had an Argonian and a Khajit, who Jordan named Amy and Rory.
The characters Cywren Caster and Papa Acachalla, from 'A Fallout Tale' and Garry's Mod respectively, both also own TARDISes, but Vahl's TARDIS appears to be less advanced than its counter parts. Ironically however, despite Vahl's fantasy-like reality, her TARDIS is the most useful of the three, as she can call it to her whim with magic and it is the easiest to control.