Almost nothing is known about Epsilon's childhood, however one thing is for sure, it was one with a lot of problems.
Ever since he was a little boy, Epsilon was a ward of The Department of Extranormal Operations's orphanage, thanks to his powers and intellect. This orphanage was top secret, and was made to take care of all young metahumans.
Although it was never fully explained what powers Epsilon has, it was shown that he had a variety of powers, including super strength, the ability to fly, immunity to magic and enhanced durability.
After Epsilon sometimes showed a psychotic personality, the D.E.O decided that it would be better to keep an eye on him even after he left the orphanage when he turned 18.
Along with his lover Theta, Epsilon worked for a mysterious benefactor. He was hired by that benefactor to join the Titans and destroy them from within. Soon after he was hired he made an appearance in New York disguised as a superhero trying to get recruited by the Titans.
Epsilon's first few superhero acts earned him the respect of city officials, but didn't get him close to his objective. After capturing Cheshire, recently escaped from prison, the D.E.O. made move to capture him. Before they could bring him in, the Titans intervened. Against the objections of tough Native American Agent Dakota Jamison, the Titans took Epsilon to Titan's Tower. Though skeptical of letting him stay, Epsilon won the Titans over when he unmasked himself without hesitation. After getting Nightwing's approval, Epsilon is allowed to crash with them. His arrival also coincided with a mysterious group of kids showing up at the Tower. Despite not being a Titan and having no connection to the children, Epsilon advocated for them to stay, to no avail. However, when the kids returned, the team relented and let them stay. At this point, Nightwing and Dakota Jamison secretly began to build a case against the suspicious Epsilon.
After spending more time with the team, things get complicated when he is dragged to a shopping trip with Argent (who is noticeably attracted with him). After finding a reminder of a meeting he was supposed to have, he brings Argent to a posh Manhattan hotel where they find Theta, a metahuman woman claiming to be Epsilon's girlfriend, even though he doesn't seem to know her. When Theta attacks Argent, Epsilon has a shift in personality, leaving Theta and Argent baffled at his strange behavior. On the way back to the Tower, Argent agrees to keep his mood swings different for the time being.
Later, the D.E.O. comes back for another shot at Epsilon, but also reveal the kids he vouched for were the agency's legal wards. Epsilon gets upset and charges in when threats start to fly, sparking a three-way fight between the Titans, the agents, and the kids. Eventually things calm down, but Epsilon has another shift that left him immobile for most of the melee. Meanwhile, Argent made a move on Epsilon, but his awkward response left her confused. Curious about his odd behavior he decides to do some investigating and learns that Epsilon and Theta were hired to infiltrate and take down the Titans. To get to the bottom of the matter, Argent calls in former Titan Lilith Clay to get to the truth out of his mind. Though reluctant, Epsilon allows Lillith to read his mind, which proves he is innocent. Once he is cleared, Argent kisses him again, but this time he is keeps his composure better, and the two later decide to pursue a relationship.
When the D.E.O. reaches out to the Titans for help with another of their wards - a boy with the power to project his mind into another person's body named Kevin Tanaka - Epsilon begins acting strangely (though it's not mood swings). Later, when he talks to the other meta children at the Tower, it's revealed his behavior at the D.E.O. is because Kevin has been possessing Epsilon for some time. However, his real body is dying, so his friends try to talk him into leaving Epsilon. Because Kevin's real body is paralyzed from the waist down, he is reluctant to part with a fully functioning body. However, when D.E.O. doctors are forced to revive his failing body, their efforts force Kevin back to his real body, leaving the real Epsilon free. Revealing his true nature and the full extent of his powers, Epsilon defeats the team, blows up the Tower, and flies off.
Last Stop - Vengeance
The first thing Epsilon does is meet up with Theta. After convincing him of what happened to him, Theta suggests that they run away. However, he boyfriend only cares about getting even with the kid who possessed him. The two then beeline towards D.E.O's orphanage. Once they get there, they engage Argent, Arsenal, Tempest, and Agent Jamison. They manage to hold their own, but Theta and Epsilon are too powerful to take down. After Argent and Theta K.O. each other, Epsilon goes in for the kill. Out of options, Kevin possesses an unconscious Argent, and uses her powers to blast Epsilon, apparently fatally. Theta wakes up in time to see Epsilon go down, and she escapes with her boyfriend's seemingly dead body.
Powers & Abilities
Epsilon's powers have yet to be fully catalogued; he appears to possess great strength, incredible durability, concussive energy blasts and the power of flight. He also seems immune to magic, as Dark Angel's spell and Tempest's eye beams have no effect on him.
Theta appears to share many of Epsilon's meta-abilities, including great strength, incredible durability, concussive energy blasts and the power of flight.