Task Force Epsilon was a Starfleet task force in the late 24th century, led by the USS Phoenix-X, only assembled for specific missions. It was previously dubbed as Flame Squad during the Dominion War, where it was sometimes referred to as a fleet. Its home port was Starbase 55. (Star Trek: Phoenix-X)
After the war, the group, not including the Phoenix-X, remained stationed at Flortarios for a year. ("Loyalties, Part I")
In 2377, the Phoenix-X stumbled upon the group working on a transceiver array with the Ceavon. The group was being led by the USS Shark and resented the Phoenix-X for not sticking around for the rest of their previous assignment. When an airborne virus from the Ceavon array affected the crew of the Phoenix-X's cognitive function, the Phoenix-X opened fire on the group. ("Loyalties, Part I & II")
Years later, in 2390, several divergent Hirogen attack ships began striking Federation starships, and Starbase 78. Several Starfleet ships from the group were thought destroyed in the attacks, not including the USS Ixion, which was re-assigned. The Phoenix-X was then called to assemble the group, now dubbed Task Force Epsilon. After receiving re-launches for those in the group that were destroyed, the group was hesitant to join; but eventually agreed to fight. Soon after, with the help of Task Force Zeta they were successful in stopping the Hirogen and discovering several Hirogen had Q Continuum-powers given to them by Qu. ("Into Harshness", "For the World is Worldly and Such")
In 2410, during the Iconian War, Task Force Epsilon was assembled to hunt down a covert group of Herald ships. With the assistance of a Herald trickster, a Thrall, the USS Dropzone set its own trap when it appeared they were being ambushed by the Herald group of ships-- In fact, it was the remaining ships from Task Force Epsilon who then dropped out of warp and backed up the Dropzone. ("Captain's Log")
- The name Task Force Epsilon wouldn't be coined until the episode "Into Harshness".