Arkad was once a pupil of Bra'tac, who always felt there was "something wrong" with Arkad. Eventually, he became the First Prime of Atum. The System Lord Apophis later sent Teal'c to attack a world called Co'rak, and Teal'c directed the Ha'taks to bombard the planet from orbit, killing Arkad's parents and sister. Arkad later arranged for Teal'c's mother to be murdered in reprisal. Over the next several years, Teal'c and Bra'tac would engage his forces, defeating him, yet Arkad would always escape. After the fall of the Goa'uld Empire, Arkad was relegated to the fringes of the various Jaffa who emerged. When the Ori crusade began, Arkad pledged himself to the Ori.
He arranged to a deal with Adria where Jaffa from Ori controlled planets would mine Naquadah for a series of bombings on Earth, leaving the Tau'ri vulnerable to attack by the Ori Army. When he learned of a summit on Dar Eshkalon intended to reform the Free Jaffa Nation, he ordered the bombing of it, killing thirty two Jaffa, and injuring several more, including Teal'c and Bra'tac. After sufficient recovery, Teal'c left Stargate Command to kill Arkad, even attacking SG-1 in the process. Teal'c was injured while heading to Arkad, who then fought Teal'c. After impaling Teal'c with a sword, Arkad took credit for killing Teal'c's mother. Teal'c kicked him onto a hook holding weapons, piercing his chest, then drove the sword through Arkad, killing him. (SG1: "Talion")
Though Arkad was dead, his Jaffa continued to follow his orders regarding the bombings on Earth. Vala Mal Doran's father Jacek learned of the coordinates for where the cargo ships holding the naquadah was located from some of Arkad's Jaffa who were having second thoughts. Plotting to sell the naquadah and split the proceeds with the Jaffa, Jacek contacted the SGC and made a deal for the coordinates. Using the information, the Odyssey located and destroyed Arkad's attack ships. Their destruction caused a significant secondary explosion that was visible from space, indicating that Arkad had mined quite a lot naquadah and would have done serious damage to Earth. Though one ship left early and reached Earth, the Tau'ri were able to locate and capture it, foiling Arkad's plot completely. (SG1: "Family Ties")