They formed a gang called the 'Disciples of Ragnos', and they started worshipping a Sith Lord called 'Marka Ragnos' who died nearly five thousand years prior. They found a staff that allegedly belonged to him and started travelling round the Galaxy draining the Force energy from different places.
Clearly this plan was as ridiculous as it sounded, but Tavion didn't seem to care. Most of her followers assumed that the staff was little more than a trinket and they only went along with it because they occasionally got to kill some Jedi - if they were able. Only the Kothos Twins had true faith in Tavion's plan.
Tavion later seduced some random Jedi failure to the Dark Side and travelled to Vjun to meet with the Kothos Twins and prepare for Galactic War. However, some Jedi infiltrated her base and attacked the converted Jedi and the Reborn. After the Kothos Twins were killed, Tavion retreated to her base on Korriban and started using the Force energy to resurrect Marka Ragnos. Amazingly, it was revealed that her plan wasn't just a load of old bollocks - she actually did own the real sceptre of Marka Ragnos. Shame he was a bitter failure. Nevertheless, he rose from his tomb and started throwing rocks around with the force.
Naturally this activity caught the attention of the Jedi and they sent Jedi Sentinels to investigate. Kyle Katarn and his students attacked Tavion's base on Korriban with a group of other Jedi and managed to drive her away from the tomb. Marka Ragnos possessed her body but was defeated by an able student of Kyle's. Kyle then used the sceptre to blast Tavion out of the tomb. With Tavion and Ragnos destroyed, everyone went home.