When the Cytherians were dying out, they created the Vepaja to watch over the Cytherians who were kept in cryogenic chambers. It was to teach the Cytherians after the planet's atmosphere was repaired and they were brought out of stasis.
Billions of years later, human colonists terraformed Venus, making it suitable for the Cytherians. Empress Vulpina happened to encounter the cave where Vepaja was kept. She claimed she would help him, but instead she released the stored species and took the Cytherians as use as slaves, calling them Thraskin. This continued for six years, until the Sixth Doctor, Jago and Litefoot came to Venus. The Doctor figured out where the animals of Venus came from and found the cave where Vepaja was. In order to protect her secrets, Vulpina followed him and tried to kill them with an explosion. Vepaja protected them, but decided this was an act of war. He used his psychic powers to cause Amtor to crash, freeing the trapped Thraskin. He then psychically controlled Shanghorns to force them to attack the survivors. The Doctor was able to warn Jago and Litefoot about the Shanghorns, who were able to put them to sleep with music. The Doctor was able to negotiate peace with Vepaja, allowing the Thraskin and Venusians to live in peace. (AUDIO: Voyage to Venus)
Vepaja was created from the greatest minds of the Cytherians and had vast mental powers. It could produce force fields, mind control thousands of Shanghorn and produce thunder storms. Because it was made of several minds, it could only act when the majority agreed. (AUDIO: Voyage to Venus)