Terrak Morrhage was a male Sith Lord who specialized in the scientific arts. Notably, Morrhage created a plague which nearly wiped out the early Jedi Order.
A Force-sensitive Humanoid, Terrak Morrhage trained as a Sith at the Academy of Sigil where he specialized in scientific applications of the dark side of the Force. Purposefully tasting poisons to build up a tolerance, Morrhage was taken under the tutelage of a female Sith Lord who was determined to see him rise to greatness. Working from his master's laboratory, the pair began developing terrible hazards for use against their greatest enemy: the Jedi Order. During his training, his master fled Sigil in fear that the Jedi Order was searching her out. Ultimately, the Jedi found the Sith woman and killed her, retracing her trail back to Sigil and burning her laboratory to the ground. Escaping the assault, Morrhage was enraged by the loss of such wisdom and vowed revenge. Decades after his master's death, Morrhage developed a plague of terrible power, designed to expose the Order's hypocrisy by turning its members to the dark side and making them Morrhage's thralls. As Morrhage infected more and more Jedi, they suffered paranoia and psychosis as the Sith Lord leached their powers and used them to increase his own strength. Amassing a huge army of thralls, Morrhage launched a war against the Jedi Order which threatened to decimate the Sith's sworn enemies. Despite the strength of his armies, Morrhage was undone by a Jedi healer who developed a shielding technique that cut Morrhage off from his victims and allowed them to think on their own again. While the healer died in the process of freeing Morrhage's thralls, they recorded the ritual for other Jedi to learn and eventually Morrhage was defeated. Killed in battle, Morrhage's servants entombed his body on Malachor III within an ancient temple where he would lie undisturbed for millennia.
Long after his death, Morrhage's tomb was disturbed by the modern Jedi Order of the age. During a time of galactic turmoil known as the Great Galactic War, the Jedi Order dispatched a taskforce of Jedi Knights to Malachor III to investigate the world. Jedi Parkanas Tark, Yuon Par, Duras Fain, Sidonie Garen, Eriz Vossan and Cin Tykan began searching the tomb for ancient records or scrolls when Morrhage's spirit awoke and began to play with the emotions of the young Jedi and drove them into a frenzy of lust and passion. While the rest of the team managed to escape to planet, Jedi Tark was left behind to be tortured by Morrhage and, eventually, Morrhage's dark spirit corrupted and possessed him. Leaching off of Tark's youth and strength, Morrhage dubbed himself Lord Vivicar and began to exact his revenge on the Jedi Order by lashing out at the Jedi who had abandoned Tark on Malachor III. These Jedi began suffering a psychosis unknown to the Jedi of the era and quickly became violent. Eventually, they were stopped by the actions of a lone Jedi Consular who had uncovered the ancient shielding technique from records kept with the Coruscant Jedi Temple's Archives. Defeated, Morrhage warned the Consular that should Tark die, all the Jedi Masters afflicted by the plague, shielded or not, would die with him and attempted to goad the Consular into striking him down. The Consular instead chose another option and used the shielding ritual to exorcise Morrhage from his host. Screaming with rage, Morrhage swore he would gather his strength and revenge himself upon the Consular before disappearing, releasing Jedi Parkanas Tark from his thrall.
- Star Wars: The Old Republic Encyclopedia