Primeval (audio story)

 was released in November, 2001. It featured a return to Nyssa's home planet of Traken.

Publisher's summary
Nyssa will die at dawn, and the Fifth Doctor doesn't even know why.

To save her life, he must make a desperate journey to the only place in the universe where a cure might exist to heal her.

When even that fails, the Doctor has a choice –­ let Nyssa die, or make a deal with the devil.

After all, the road to hell is paved with good intentions...

Plot
to be added

Cast

 * The Doctor - Peter Davison
 * Nyssa - Sarah Sutton
 * Shayla - Susan Penhaligon
 * Kwundaar - Stephen Greif
 * Sabian - Ian Hallard
 * Anona - Romy Tennant
 * Janneus - Rita Davies
 * Hyrca - Mark Woolgar
 * Narthex/Captain Kabe - Billy Miller
 * Etrayk - Alistair Lock

Continuity
This story portrays the planet Traken several thousand years before The Keeper of Traken. In this era the Source exists but there is no Keeper. It is revealed that in the distant past the people of Traken worshiped and were ruled by the entity known as Kwundaar, but rebelled against him and built the Source as a means of driving him away. What Kwundaar is is never explained, but he can see and manipulate events across time and space and knows about Traken's eventual destruction. The Source's attack has left him burnt and deformed. He now dwells on a spaceship on the edge of its influence, waiting for a chance to retake control. Kwundaar tries to seize control of the Source by installing the source manipulator, leading to the installation of Shayla (and briefly the Doctor) as the first Keeper.

This story reveals that Nyssa's collapse in Kinda and the telepathic powers she demonstrates in Time-Flight are the results of Kwundaar's manipulations. Seeking to regain control of the Source, Kwundaar needed to use a native of Traken who had left the union. He chose Nyssa. Ultimately, it is the Doctor whom Kwundaar wants to use to destroy Traken.

Timeline
The Impossible Astronaut Day of the Moon The Curse of the Black Spot
 * Primeval occurs after BFA: The Mutant Phase
 * Primeval occurs before ST: The Parliament of Rats