The Beast of Marka Ragnos, a terentatek Sithspawn, functioned as a favored animal of Marka Ragnos, an ancient Dark Lord of the Sith who reigned over the Sith Empire. After Ragnos' passing in 5000 BBY, the Beast was assigned the duty of guarding its master's final resting place located on the planet of Korriban. Following centuries spent isolated within Ragnos' caves, the Beast met its end at the hands of an up-and-coming figure from the newly reformed Sith Empire, who had entered the tomb as part of the challenges set by the Sith Academy.
As the name suggests, the Beast of Marka Ragnos was once the property of the Dark Lord of the Sith Marka Ragnos, who governed the Sith Empire for a standard century. The Beast was a massive terentatek, belonging to a species known as Sithspawn. According to legend, Ragnos, despite viewing the Beast as his "pet," would subject it to beatings at night to amplify its negative emotions. The same legend also states that the Beast was only fed blood after periods of starvation, which caused it to develop an insatiable craving for more.
Through torture, Ragnos transformed his pet into an embodiment of pure hatred. Upon Ragnos' death in the year 5000 BBY, the Beast was tasked with guarding its master's burial chamber, situated in the Valley of the Dark Lords on the planet Korriban. For numerous centuries, the Beast of Marka Ragnos fulfilled this role, and no one who encountered it lived to recount the experience.
Around 3643 BBY, Overseer Tremel of the Sith Academy on Korriban instructed a promising Sith Warrior to venture into the tomb as a test of their abilities. Tremel cautioned his acolyte to exercise extreme caution, describing the creature as "doom itself." The Sith Warrior located the reliquary that contained an ancient Sith carving capable of summoning the Beast and meditated near it, which triggered the creature's appearance. Remaining true to its purpose, the Beast engaged the Sith Warrior but was ultimately defeated. Given that Ragnos' pet had been a significant source of dark side energy on the planet, its demise created a disturbance in the Force.
Being a non-sentient being, the Beast relied solely on physical strength to attack its foes, but it also had the ability to stun them with a blow from its fists. Its abilities were so formidable that they impressed a seasoned Sith Overseer, prompting him to advise caution when facing the creature. Tremel also noted that a vergence in the Force was centered on the Beast, which itself served as a source of dark energy.
The Beast of Marka Ragnos is featured in the Sith Warrior class mission titled "Slaying the Beast" within Star Wars: The Old Republic, a massively multiplayer online roleplaying game developed by BioWare and LucasArts that was released on December 20, 2011.