Keeper of Traken
The Keeper of Traken, or simply The Keeper, was the leader of the planet Traken and of the Traken Union. The Keeper had the power to control everything in the Union, making sure everything was harmonious.
The first Keeper was The Doctor. He defeated the inventor of the Source, Kwundaar. He gave the title to Shayla, who held it for an unknown time. (BFA: Primeval)
The Keepers ruled for thousands of years with the power of the Source. The Source allowed Keepers to take control of minds and to materialise anywhere. Drawing on all the minds of the Union, they protected the planets. Every thousand years, a new Keeper would be chosen when the old one died.
As his end approached, the Keeper contacted the Fourth Doctor for his help. He explained about the Melkur on Traken and asked for help preventing the evil from taking control of the bioelectronic Source that was the keystone of the Keeper's power and of Traken civilisation. The Doctor and Adric agreed and the Keeper pulled the TARDIS to Traken.
The Keeper had chosen Tremas as his successor. When Tremas came under suspicion with the Doctor and Adric about the Melkur, Kassia was chosen by the consuls to replace him. However, she was working with the Melkur.
When the Keeper died, Kassia became connected to the Source. Immediately, she was taken over by the Melkur, who became the new Keeper. Adric and the Doctor sabotaged the connection to the Source and forced Melkur out of the Keeper's sanctum, allowing Luvic to take Melkur's place and become the new Keeper of Traken. (DW: The Keeper of Traken)
When a wave of entropy swept across part of the universe, Traken was destroyed. The Keeper died with the planet and the rest of the Union. (DW: Logopolis)