When the Goa'uld first arrived on Earth, Sokar began to align himself with the personas of various underworld demons, including the Biblical Satan. During that period, Sokar held an Unas host, though he eventually moved to a human one. For a time, Sokar was ruler of the Goa'uld, until an alliance consisting of several other System Lords, including Ra, Apophis, and Cronus, banded together to defeat Sokar. He was believed destroyed, but somehow survived. He later conquered the world of Delmak, making it his homeworld, and pyroformed its moon into a hell-like world, naming it Netu. His underling Bynarr ruled Ne'tu, traveling to Delmak by way of Rings to inform Sokar of the suffering of the damned.
In 1999, he made his presence known again among the System Lords, by making Apophis a prisoner on Netu, as well as engaging in a war with Heru'ur. All while somehow amassing a tremendous fleet granting him power he had not held since his defeat by Ra's alliance. (SG1: "Serpent's Song", "Jolinar's Memories")
Within a year, he was prepared to launch a massive attack against the System Lords, which he hoped would have put him in control of the Goa'uld Empire. Realizing how dangerous that would be, during the Battle of Netu, the Tok'ra destroyed Netu while Sokar, aboard his orbiting Ha'tak, attempted to put down a rebellion begun by Apophis when SG-1 arrived attempting to rescue Jacob Carter. When Sokar arrived, Apophis promised him valuable information in exchange for sparing his life and elevating him to a lord, though really he intended on assassinating him. Sokar allowed an audience and used the rings to transport Apophis to his ship. Apophis told Sokar of a Tok'ra base location, but not knowing that there was no base. Sokar, however, had recently conquered the planet, finding no Tok'ra, and ordered Apophis to be tortured to death. After the Tok'ra launched the explosive into the core of Netu, Sokar's Jaffa informed him of the instability, and Apophis used the chance to kill the two Jaffa with his hidden blade. Sokar tried to use his kara'kesh on Apophis, but Apophis used the staff weapon, forcing Sokar to activate the shields and Apophis fled. Sokar was killed when his ship was caught in Netu's explosion, but Apophis escaped by transportation rings and took control of his forces. (SG1: "Jolinar's Memories", "The Devil You Know")
Aside from the standard Goa'uld traits of arrogance and egotism, Sokar was made infamous for his sadism and cruelty, which were greater than just about any other Goa'uld, aside from Anubis. Sokar would frequently torture people right in front of him and took extra pleasure in prolonging the suffering of his victims to the point of maniacal laughter. This happened to both Jolinar of Malkshur and Apophis during their incarceration on Netu.
Sokar apparently had a fair sense of the Tau'ri version of Hell, and so inspired by it, formed his prison world by bombarding the moon from orbit to crack the mantle and allow magma to seep to the surface and turn the sky red. He also was shown to have a militaristic viewpoint on a lot of topics, preferring to dominate via his army. Like other Goa'uld, he had a flair for the dramatic. His speech was twisted, and he usually had a flame nearby.