A Federation colony close to Tzenkethi space which, in The Adversary, is reported to be under attack, a report that draws the sabotaged Defiant further towards the border.
Barisa Prime is a Federation colony world lying near the frontier with the Tzenkethi.
In The Adversary, while the Defiant is patrolling that frontier at the urging of the supposed Ambassador Krajensky, the ship picks up a distress call saying that the colony has come under Tzenkethi attack before communications are cut off. Sisko sets course to help, only to discover that the Defiant's systems have been comprehensively sabotaged by a Changeling hidden among the crew.
The report forms part of the infiltrator's effort to manoeuvre Starfleet into firing the first shots of a new war. The colony is never shown on screen.