The Detrion system was a star system in the Alpha Quadrant. It originally contained nine planets, including Detrion 9. Another of its planets possessed a dense ring system composed of dangerous icy debris.
In 2381, Nick Locarno established Nova Fleet, consisting of starships whose junior officers he had incited to mutiny, in the Detrion system. To protect his new domain, he had erected a trynar shield around the system, which he claimed was indestructible. In a public announcement, Locarno invited like-minded ship crews to join him in the "forgotten" system. As further insurance against incursions, he revealed that he had a black market Ferengi-made Genesis Device in his possession.
In a blow to Locarno's plans, Lieutenant jg Beckett Mariner seized the Genesis Device and fled in the USS Passaro, but quickly realized that the trynar shield had trapped her within the system. She evaded Nova Fleet until she was cornered by Locarno inside a level 7 ion storm, leaving her no choice but to activate the Genesis Device. Locarno refused to evacuate, believing that he could disarm the device; however, he was thwarted at the last second by a paywall, and was killed in its detonation. The explosion restructured the ion storm into a new, tenth planet that would come to be named Locarno. (LD: "Old Friends, New Planets")