The Vorassan Cult were a cult from Tarron's early history.
The Vorassan cult believed that Tarron rejected the colonists because they had too much of an "Earth spirit".To fix this, they believed that the spirits had to be released with a treppaning. To be properly prepared, the victim was kept conscious for the process. If Vorass himself took part, he would carve a "V" on their back.
The Vorassan Cult was started by Akha Vorass (also known as Danta Vorass) when he left the colony and went into the wilderness. With a combination of the vegetable dyes and the natural radiation of the planet, he went mad. He killed Marran and converted Garva, her husband and the new leader of the colony. The cult continued to grow, since he distributed the dyes necessary for the conversion. Eventually, he was stopped by the Azmec Corporation
Centuries later, the Azmec Corporation stole Akha from the past using a Time Scoop and sent him to kill certain members of Tarron society. When these murders attracted the attention of the First Doctor, they also tried to kill him with Akha, but the Doctor returned him to the past. (PROSE: Tarnished Image)