In 2371, Starfleet Intelligence believed that the Cardassians were secretly building a fleet in the Orias system, without the knowledge of the Central Command. The Maquis feared that this build-up was a prelude to a new offensive in the Demilitarized Zone, and so Thomas Riker stole the USS Defiant to investigate. He was prevented from entering the system by several Keldon-class warships fielded by the Obsidian Order, though he did provide the Central Command with scans of the system in exchange for clemency. (DS9: "Defiant")
According to Star Trek: Star Charts (p. 46) and Stellar Cartography: The Starfleet Reference Library ("Stellar Cartography", p. 18; "Federation Historical Highlights, 2161-2385"), the Orias system was a binary system with a M-class star and a K-class star. According to a map of the Cardassian Union – prepared by an anonymous astrography clerk, from the Cardassian Central Archives, in 2364 – Orias was identified as a Cardassian system.
According to the script, Orias was pronounced as "o-RYE-us".