Never Vault
From Tardis Wiki, the free Doctor Who reference
The Never Vault was a location once visited by the Master and the Supreme Dalek around the slopes. They fought each other at that point, but both survived the meeting.
Years later, Missy told a Skaro Dalek about the encounter, asking if its Supreme Dalek was "the same old". (TV: The Witch's Familiar)
The War Doctor led the final charge up the slopes of the Never Vault. (PROSE: The Day of the Doctor)
