Belus was a Goa'uld System Lord who served under Ra. After leading a failed invasion of Oannes, he incurred the wrath of its native people, the Ohnes, and was punished for his failure by being sent to oversee Goa'uld forces in Babylon. When an Ohnes team followed him to Earth, they were able to encourage the local populace to rise up against Goa'uld rule, causing him to be further punished by demotion to an underling of Ishtar, a position he continued to hold after Ra's death. He was later wounded by Kel, and so took the Ohnes warrior as a new host, an act which he saw as revenge against the Ohnes.
During Belus's early years, his accomplishments among the history of the Goa'uld were not noteworthy. He once served under the Supreme System Lord Ra, during which time he achieved moderate success in battles. It was perhaps due to these successes that Ra bestowed upon Belus a small domain within his own empire, allowing Belus to act more or less autonomously, due to the fact that his actions had little to no real consequence on Ra's overall plans. Despite having no real power of his own, Belus managed to rise to the rank of System Lord during this time.
Invasion of Oannes
This all changed when Belus discovered a new planet; Oannes. Having discovered that the planet was home to a native species—the Ohnes—Belus chose to bombard their cities from orbit, driving them from their homes and making them easier to capture. Belus already had his own slavers on the surface, who easily captured thousands of the Ohnes and transported them to Belus's ships, which were waiting in orbit. Confident that he had achieved victory, Belus only left a skeleton force behind on the planet, and planned on returning to his empire with the newly captured slaves.
However, Belus's ship was but a single day away from the planet when the Ohnes on board rebelled and overwhelmed their captors, moving to seize control of the ship. Belus was quick to flee his overrun ship with only his First Prime in tow, but was able to engage the ship's self-destruct system before doing so, ensuring the deaths of thousands of Ohnes on board. At the same time, the Ohnes who had been left on their home world rebelled against the Goa'uld and Jaffa who had been left behind, quickly retaking their planet. Before killing all their captives, however, the Ohnes were able to extract the location of Con'Tora through use of their memory retrieval technology. With this knowledge, a group of Ohnes warriors journeyed through their Stargate within days, intent on rescuing their captured brethren.
Upon arriving, however, they were immediately set upon and captured by Belus's Jaffa, then brought before Belus himself. In the hopes of intimidating the rest of the Ohnes, Belus ordered all but one of the attack force to be slain, sending the lone survivor back through the Stargate along with the dead bodies. Although Belus thought that this would incite fear in the population when the survivor told the rest of his kind about Belus's vicious nature, it did little more than ignite a burning passion to confront and defeat the Goa'uld within them. Within days of receiving Belus's message, the Ohnes managed to perform a series of strikes against Belus's forces on his home world, crippling most of his spaceships and slaughtering thousands of his Jaffa, over half of his overall forces. Belus was left with little choice but to flee from the Ohnes once again.
Ruler of Babylon
It was due to this failure that Ra sent Belus to Earth in order to rule over the forces occupying Babylon, a duty which was considered fairly ignominious, and was deemed a fitting punishment for his repeated failures. Even in this task Belus was unable to escape the relentless Ohnes; a small team of freedom fighters—led by Omoroca—were sent to his new kingdom within a matter of years. Though their ultimate task of driving the Goa'uld from Earth failed with the death of Omoroca and the capture of Kel—another Ohnes warrior—they were able to cause the local populace to rise up against their false gods.
Once again finding himself on the verge of defeat, Belus ordered those Jaffa who remained loyal to round up any slaves they could so that he would be able to escape. Taking Kel as his personal trophy, he took the captured Humans to a new world which he named Akkad after the fledgling civilization on Earth. Upon his return to Goa'uld space, however, Belus was punished by Ra for his repeated failures. No longer a System Lord, Belus was sentenced to serve under Ishtar, an underling of Ra. Though Ishtar gave control of Akkad over to another Goa'uld—Sargon—he allowed Belus to return to his former home world to manage the productive naquadah mines. Despite being a prisoner, Kel was able to once again launch an attack on Belus within weeks of the two arriving on Belus's home world. This attack ultimately failed, as Kel was unable to damage Belus's symbiote, but it severely damaged his host. It was because of this that Belus chose to transfer himself into the Ohnes warrior rather than kill him, forever imprisoning the Ohnes warrior. This particularly pleased Belus, as he knew just how much Kel hated the Goa'uld.
After hearing of Ra's death, Belus saw another opportunity to gain power but it, like his previous attempts, ended in failure. As such, Belus continued to serve under Ishtar, confined to his stronghold, though he was sent on the occasional minor mission for Ishtar. A broken Goa'uld, Belus's only pleasure came from knowing that Kel was suffering just as much as he was. Ishtar continued to allow Belus to oversee one of his naquadah mines, an operation which Belus considered to be extremely tedious, though it kept him too occupied to plot any further mischief. Due to his previous defeats, Belus believed that the Ohnes were responsible for most of his problems and so harboured a continuing grudge against them. The Jaffa in Belus's service were given standing orders to attack any Ohnes on sight and bring them before their master for slow and leisurely torture. (RPG: "Fantastic Frontiers: Stargate Season One")
During the first year of the Tau'ri's Stargate Program, Daniel Jackson was captured by Nem—Omoroca's mate—on the planet Oannes. Nem, wishing to know the fate of his mate, used his species' memory retrieval technology to bring up Daniel's knowledge of the Babylonians. It was only then that Nem learned Omoroca's fate, while Daniel learned that Belus had been a Goa'uld. Though both men realized that Omoroca's mission had ultimately been a failure, Daniel acknowledged that the Tau'ri owed Omoroca a great debt for helping them overthrow the Goa'uld. (SG1: "Fire and Water")