Crassus Prime was the Secondary moon Oricon, a moon in the Outer Rim Territories just outside the Seat of The Empire.
An insignificant world, it was home to Darth Torren, before its location was lost to the wider galaxy. Torren experimented with Sith Sorcery and Alchemy on the world, creating monsters, artifacts and even plants strong with the dark side. Darth Torren later died from a failed expiriment and his compound was destroyed, and his descendants later claimed the planet and joined in the Dread Master's Cause..
During the era of the reconstituted Sith Empire, the Dread Masters: Bestia, Tyrans, Brontes, Styrak, Calphayus, and Raptus used Darth Torren's home, and with the Dread Guards help created a citadel for training Dread Guards who had no prior training and created a Holocron with the secrets of the Dread Masters and the Dread Guard and contained the holocron inside the Holocron Tower.
During the Galactic War, the Dread Masters' rebellion against the Empire was brought to end in the Dread War on Oricon, where the remaining Dread Masters were slain within their fortress as well as the Dread Guardsmen on the planet, Remaining Dread Guard on Crassus attacked the Empire on Oricon but none survived and those who may possibly had survived were either imprisioned or went into hiding. One survivor who didn't surrender to the Empire, was Naishas Ari, going under the Alias of Tya Kieran.
Lord Emperor Veldarius of the Sith Imperium found the young Naishas Ari on the planet as well as the Holocron Tower, and took both into the Imperium Capital of Solaria.