Darth Decimos was a Siniteen Sith Warrior who was active in the Old Republic era. Because of his notable skills in battle, his fighting styles were programmed into a holographic simulacrum, for use for training Padawans. The simulacrum survived the destruction of the Jedi Temple and was later salvaged by the New Jedi Order.
Biography
Sith Empire
Darth Decimos was originally part of Exar Kun's Sith Empire, but following its near total destruction at the hands of the Republic, he went into hiding. With the emergence of a new Sith Empire, Decimos immediately joined it, pledging total loyalty to Darth Revan, and later Darth Malak. He was known for his ferocious combat skills and was greatly feared by both the Jedi and his fellow Sith for his sheer bloodlust. He was present for the Battle of Rakata Prime, where he was part of a boarding party that was sent to destroy a Hammerhead-class capitol ship. While a number of Sith troopers planted explosives on the core components of the sip, Decimos held off the crew, mercilessly slaughtering anyone who got in his way. However, as he was doing so, he witnessed the destruction of the Star Forge and sensed Darth Malak's death. Knowing that the battle was lost, he reached an escape pod and jettisoned it, but not before planting explosives into the other escape pods.
Genocide
Decimos crash-landed on Lehon, and was pleased to notice that there were a great deal of other Sith there as well. He rallied up the survivors and began planning a counterattack on the Republic. However, he noticed that there were also a number of Sith assassins present. Decimos, having an intense dislike for Sith assassins, ordered the Sith and Sith troopers loyal to him to kill all of the Sith assassins present. However, his plan was met by opposition by Darth Deimos, the leader of the Sith assassins on Lehon and Darth Wraith, who released that if they were to launch a counterattack on the Republic, then they would need all of the soldiers they could find. A battle raged between Decimos and Deimos' forces while Wraith attempted to reason with Decimos and his soldiers. Wraith was eventually able to convince Decimos to stop the battle, explaining that they would need the soldiers. However, the damage was done, the majority of the Sith assassins on Lehon had been slaughtered, and Decimos' soldiers had taken moderate casualties.
Battle of Lehon
A few days after the infighting, the Republic began a cleansing operation on Lehon. Decimos, Deimos and Wraith made strategies to deal with the enemy. They activated a deflector shield generator that would prevent the enemy from orbitally bombarding their island base and would force them to send down dropships. Using this time, they began preparing their troops. Wraith would coordinate their soldiers from a command post while Decimos lead the ground forces and Deimos lead an aerial assault. Decimos leapt into the fray and cut down Republic soldiers left and right, dealing heavy casualties. However, despite his battle prowess, the Sith were losing and taking heavier casualties. Wraith, realizing this and knowing that he would be executed if he were to be captured, activated a colossal Rakatan tractor beam to pull down a Republic ship in a massive kamikaze attack. He deactivated the planetary shield and pulled one of the Republic's Hammerhead-class capitol ships down to the island. Deimos, realising what Wraith planned, attempted to escape from the ship, but his fighter was destroyed in the resulting blast. However, he survived, albeit with grievous injuries. Decimos meanwhile witnessed the event and rather than vainly attempting to flee as both his own soldiers and their enemy were attempting, he merely deactivated his lightsaber, raised his arms and laughed at his oncoming demise. The shockwave sent him flying before he was vaporized in the blast.