PSX-394 was a planet in the Milky Way galaxy which contained a Stargate. It was once used as an outpost by the Goa'uld but, at some point in time, the Tau'ri of Stargate Command were able to capture the planet. From this time onwards, they used the Goa'uld outpost as a penal colony, incarcerating the prisoners which they considered to be too dangerous to keep on Earth in it. The inmates eventually managed to stage a successful rebellion, however, taking over the colony and naming themselves the OP-CORE, running their own Stargate Program from the base which they designated "The Castle." (Stargate Worlds)