P3X-584 is a planet which Anubis conducted experiments regarding Khalek, a genetically engineered human with Goa'uld DNA. SG-1 originally traveled to the planet to investigate a gravitational disturbance that Lt. Colonel Samantha Carter found. The disturbance was later discovered to be a normal black hole rather than a possible Ori Supergate.
Soon after arriving on the planet, however, they stumbled upon Anubis' lab. They found Khalek and brought him back to Earth. Dr. Daniel Jackson and Teal'c stayed on the planet and Daniel translated the logs (written in Ancient); from them, he learned that Khalek was not a prisoner of the Goa'uld but was actually created by Anubis. While they were holding Khalek, Daniel, Carter and Teal'c ran a simulation using the DNA manipulation device and discovered that Khalek could not ascend without a few more treatments in the machine. Before he could return to the planet to do so, Khalek was killed. (SG1: "Prototype")