Opus was born sometime before the fall of the Republic. His Force-sensitivity led him to be trained as a Jedi. He eventually attained Mastery and also successfully trained a Padawan, Sember Vey, to Knighthood. During that time, Opus became acquainted with Vey's friend and fellow Padawan, Feyra Akaris, before she failed the Jedi Trials and left the Order. He and Vey later felt her death in the Force. Opus supported Vey's promise to Feyra to see that her daughter, one year old Iskat, became a Jedi.
Throughout Iskat's training as a Jedi, Opus served as one of her mentors, even after Vey took her as a Padawan. Both he and Vey sought to quell Iskat's unbalanced nature, hoping to help her avoid her mother's failure. They and the Jedi Council also made sure that Iskat never learned about her mother or her home planet, going so far as to eliminate any physical record.
In 22 BBY, at the height of the Separatist Crisis, all Jedi were recalled to the Temple on Coruscant. After Knight Obi-Wan Kenobi was taken prisoner while on Geonosis, an assault team was dispatched to rescue him. While Master Mace Windu led the main force in infiltrating the Petranaki arena, Opus was tasked with taking a small contingent of Padawans and their masters into the stands to eliminate Geonosian guards and cannons. The group included Vey and Iskat. During the fighting, Iskat saved Opus and a fellow Padawan from the enemy, but her brutal style of fighting disturbed the Jedi Master. After their mission was complete, Opus called a retreat from the greater battle, during which Vey was killed. Opus pulled Iskat away from her dead Master, insisting that they had no time to recover his former Padawan's body.
Opus fought in a number of missions throughout the resulting Clone Wars. Whenever he had time back at the Temple, he took the opportunity to train with Iskat, who had been grounded by the Council in the aftermath of her mission to Thule. A few years later, he and Master Uumay Hawlatha spoke to Masters Yoda and Windu on her behalf, after which she was placed back in the field, being sent on missions to Olgothon 3 and Frong.
In 19 BBY, Darth Sidious enacted Order 66, which saw to the deaths of most Jedi. Opus and one of Iskat's peers, Charlin Plaka, were separated from their clone troopers when the order was issued. They soon received a signal from the Temple, ordering all Jedi to return. They managed to steal a shuttle and an old contact told them to hide on the planet Firrhana. However, the advice was actually a betrayal and they were eventually captured by the bounty hunter Jakadis, who imprisoned them in his stronghold, a former . There the two were weakened by starvation and the strong presence of the dark side.
Sometime before 14 BBY, Opus managed to escape from his cell and, on his way out of the fortress, attempted to get his lightsaber out of a heavy stone chest. He was found there by Iskat, now an Inquisitor, who cut his shackles and helped him retrieve the weapon. She mocked his joy at seeing her alive, claiming that according to the Jedi tenets he espoused, dying and becoming one with the Force was supposedly no worse. Realizing that his former mentee had fallen to the dark side, Opus begged Iskat to reconsider, telling her details about her mother that she had been unable to discover for herself. However, Iskat rejected his explanations for his and Vey's actions, arguing that they were not truly the will of the Force, as Opus claimed, and blaming the Jedi for Feyra's suicide, as well as the many deaths caused by the Clone Wars.
After Iskat attempted to Force choke him, Opus engaged the Inquisitor in a duel, she using her mother's lightsaber. At first, he attempted to stall for time, suggesting that they establish a better Jedi Order, until Iskat told him that she had already killed Plaka in her cell, mocking his cowardice since he had not tried to free his fellow Jedi. With his remaining strength, Opus went on the offensive until Iskat surprised him by pulling her concealed Inquisitor lightsaber off her back and slashing him across the shoulder, disarming him. She then decapitated him with both sabers, sardonically rejoicing that he was now one with the Force.