From Bravo Fleet Infobase
An Unidentifed Mercenary Group operating in the territory recently occupied by the Ariel Nebula creature. The organization was responsible for pulling this unique sapient life-form from a different dimension into our own in mid-2384, manipulating it for purposes still unknown using research stolen from Federation interests. The group was also responsible for the assault on and capture of Research Station Ariel, also in 2384.
One mercenary, a defector known as "Stingray", revealed that the mercenaries were, in fact, working for another entity. The extent, nature, and composition of that individual or organization is as yet unknown, but, according to Stingray, "I could tell they didn't like the Federation." They have been placed on the Starfleet terrorist watch list, but, with so little known about them, it is likely that further encounters will be at the mercenaries' leisure... or the whim of their unknown backers.
The name "Ariel Mercenaries" is an informal name, used because the group's real name is unknown and the Federation's only point of contact with it to date has been within the bounds of the Ariel Nebula.