Dark Gallifrey: The War Master, Part 1

Many have sought the legendary Dark Gallifrey over the millennia... but most have been lucky enough to fail. There is another who has his eyes on that glittering prize, however; one who knows how such power could be wielded – the Master himself!
Intrigued by rumours of a hidden Gallifrey – the Dark Gallifrey of Time Lord myth – Bernice Summerfield resolves to find it.
But as the Doctor points out, some things should never be found, and some doors should never be opened. Especially ones that want to be…