A "family heirloom" according to an alternate version of the Doctor, the TARDIS was used by the Doctor to kidnap General Sontar and the Rutan representative after he'd fitted a Time regulator into the console to construct a primitive Time Scoop which he patched into the Capitol's architectural configuration system in order to show them what the potential outcome of their never-ending war could have on the universe.
The TARDIS took the Doctor and his unwilling passengers into the far future to show the two ancient enemies the outcome of their war, to the year AD 100,000,000,000,000,000,000,000,000,000,000 where they saw nothing but devastation to make them both realise their war, no matter what they did, would only end with nothing but destruction.
The TARDIS had a working state of grace; this was instrumental when General Sontar snapped the Doctor's neck in a fit of anger. The TARDIS prevented the Doctor's death, which meant the Doctor didn't need to regenerate.
Eventually, when Omega tried to take his revenge, the Doctor was forced to abandon the two inside his TARDIS. Sontar, not learning from his failure, attacked the Rutan, who retaliated. Together they killed each other several times before they realised it was futile. Finally, after the two realised they weren't getting anyway, they both began to speak to each other.