Orias system
The Orias system was a planetary system in Cardassian space with one supposedly uninhabited M-class planet – Orias III.

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  to investigate. He was prevented from entering the system by several  warships fielded by the Obsidian Order, though he did provide the Central Command with scans of the system in exchange for clemency. ()

It eventually emerged that the Obsidian Order was building the fleet in preparation for a joint operation with the Tal Shiar to destroy the Founders in the Gamma Quadrant. ()

Appendices

Background information 
This system's quadrant of origin is inferred based on the position of the Cardassian Union as seen in the star chart appearing in the  episode . 

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". 

According to StarTrek.com, the name of the Orias system's primary was Orias.

External link 
 

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Star systems
Cardassia