Isis was the Egyptian mother-goddess and consort of Osiris. She and Osiris were influential Goa'ulds who were "banished to oblivion" by Seth when their symbiotes were placed in sealed canopic jars which functioned as stasis chambers, and were buried for thousands of years in an Egyptian temple. The jars were recovered as artifacts in 1931 by the Stewart Expedition, and were later put on loan to a Chicago museum where they were studied by Dr. David Jordan. Although the symbiote of Osiris had survived to take a new host, the seal on the Isis jar had been broken, and the symbiote inside had died.
Episode Reference: The Curse