The Hromi Cluster was a region of space near the Acamar system. The Federation had charted, but not explored, several M-class planets in this cluster, including Gamma Hromi II. In 2366, the USS Enterprise-D entered the Hromi Cluster to locate a Gatherer outpost. (TNG: "The Vengeance Factor")
Background information Edit
In the backstory to Star Trek Online, in 2404 the Klingon Empire's Chancellor J'mpok (β) invoked ancient Klingon claims to the Hromi Cluster and demanded that all Federation citizens evacuate within three months. The Federation refused, and in 2405 the region became the first battleground of the Federation-Klingon War of 2405-2410 (β).
In the game proper, the cluster is located in the Pi Canis sector block (β) and features various missions and duty officer assignments.