With the merciless Melkur in control of The Source, the Doctor and his allies have only a slim chance of deposing him, which also puts the peace of the Traken Union in severe jeopardy.
Did You Know?
[looking at Melkur sitting on the throne
Who are you?
Your new Keeper.
This is no Keeper of Traken.
Well, I know it's not exactly what you had in mind, but now, I'm afraid, you're rather stuck with him.