From The Stargate Omnipedia
Delmak is a dark world inhabited by whatever Goa'uld
happens to be in power there.
The planet is fairly technologically advanced, as much of its surface is covered by fairly sophisticated structures. It is orbited by the prison moon Ne'tu.
The world was once home to the Goa'uld Sokar and his massive armies. When Sokar was defeated, Apophis seized control of his forces and made it his homeworld.
HOME TO - Jaffa
FIRST APPEARED - Jolinar's Memories
Jolinar's Memories - SG-1 and Martouf infiltrate the prison moon of Ne'tu, in orbit of Sokar's homeworld of Delmak.
The Devil You Know - Sokar journeys from Delmak to Ne'tu, prepared to discipline the moons population. Apophis escapes to Delmak and seizes control of Sokar's army when Sokar is killed.
Enemies - Unable to decelerate Cronus' mothership, Apophis, in a flame of rage, plummets to his destruction in the atmosphere of Delmak.