Zipacna is a Goa'uld. Zipacna was a god of Mayan mythology and was considered the demonic personification of the Earth's crust.
Zipacna was originally an Underlord of Apophis. When Klorel was placed on Triad to determine priority of the body of Skaara, Zipacna served as his Archon, initially attempting to win the debate by claiming that Skaara was 'dead' already, apparently convinced that nothing of the host survives after the Goa'uld takes control. When SG-1 successfully refuted this argument, Zipacna used their argument as proof that both host and Goa'uld could survive in the body, but Klorel could not survive on his own.
Zipacna actually used the proceedings to "tag" each of the Tollans ion cannons in preparation for an attack on Tollana. When Skaara was awarded priority, Zipacna ordered his Ha'tak to attack. Teal'c and the Nox Lya hid one of the Ion cannons, and used it to destroy the mothership, though Zipacna escaped through the Stargate. Zipacna was referred to as "Zippy" by Colonel Jack O'Neill. (SG1: "Pretense")
After the death of Apophis, Zipacna managed to carve out a small domain for himself with his own fleet and armies, but lacking sufficient power to be an independent minor Goa'uld, he entered into the service of Anubis, using his resources to further his master's goals. He extended Osiris the offer to represent Anubis at the High Council of System Lords. Zipacna himself led an attack on the Tok'ra base on Revanna, searching for the symbiote poison. The poison was eventually used to allow SG-1 and Selmak to escape through the Stargate, though virtually all the Tok'ra were killed in the attack. (SG1: "Summit", "Last Stand")