The Vault (The Pilot)

A secret vault was hidden beneath the campus of St Luke's University in Bristol which the Twelfth Doctor made a promise to protect.

By the 2010s, the Doctor and Nardole had spent almost seventy years guarding the vault, while also working at the university.

The Doctor and Bill Potts were chased to the location of the vault by a puddle of sentient oil which had taken on the image of a former student. At this time, the Doctor and Nardole only left their posts when they realised that the threat was after them and showed no interest in the contents of the vault. (TV: The Pilot)