Orias III was the third planet in the Orias system. This system was located in Cardassian space in the Alpha Quadrant. The planet was the only M-class planet in the system, though it was desolate and uninhabited.
In 2371, the Obsidian Order began a covert military build-up at Orias III, in a joint venture with the Romulan Tal Shiar to attack the Dominion. Believing the Cardassians were preparing an offensive against the Maquis, Thomas Riker attempted to attack the planet with the hijacked USS Defiant. However, he was met by a force of six Keldon-class warships and chose to surrender to the Central Command. (DS9: "Defiant")
The Obsidian Order effectively prevented any further inquiries into their activities at Orias III, and later that year the combined Cardassian/Romulan fleet disembarked for the Gamma Quadrant. (DS9: "Improbable Cause")