Sonic & Sega All-Stars Warzone/Epsilon-Eagle

Epsilon-Eagle is the main protagonist of Alien Soldier. He appears as a DLC character in Sonic & Sega All-Stars Warzone.

General
In the year 2015, the planet Sierra (A-Earth in the Japanese version of the game) was gripped by fear, in the midst of a crisis of their own making. The terrorist organization, Scarlet, possesses the power to prevent humans from travelling to and from the outside universe. Consisting of artificial beings created through superior genetic engineering by the Sierrans and lead by Epsilon-Eagle, Scarlet is an underground faction seeking to destroy the human race. With super intelligence, fearsome strength and parasitic abilities allowing them to live within humans, machines or animals, they conquered the Sierrans and stood on the brink of supremacy over the planet.

The Sierrans target Epsilon-Eagle for an assassination attempt, sending a special combat group armed with superpowers to carry out this mission. The Sierran combat group launched a surprise attack on Scarlet, and Epsilon became seriously injured in the assault. Because of both factions using their abilities, the time-space continuum was opened, with Epsilon getting thrown into it.

In the confusion, Xi-Tiger took over as the head of Scarlet and began ordering more frequent and brutal attacks on the Sierrans that the other members despised him, wanting for Epsilon to be re-instated. Unpopular with the other Scarlet operatives, Xi-Tiger set out to assassinate Epsilon by activating the time-space continuum, launching an attack on the Sierrans' research laboratory, where kidnapped children with superpowers were kept for experimentation.

A young boy named Fou has Epsilon living inside of him as a parasite, but what struck Xi-Tiger odd is the fact that he could not sense Epsilon's evil. With that, he takes a young girl named Kaede hostage, demanding for Epsilon to reveal himself or else he would kill her. Fou flew into a rage, transforming into Epsilon-Eagle, now in the form of a bird-man with steel wings.

Sensing an unknown power within Epsilon, Xi-Tiger fled, but not before killing Kaede. Epsilon went off in pursuit of Xi-Tiger. However, Epsilon was not the only creature of his kind, as a similar bird-man was also created. Although their bodies are identical, the other bird-man has evil intentions. He too flew off in search of Xi-Tiger...

Trivia

 * According to the Japanese materials of the game, the Epsilon that the player plays as in Alien Soldier is Epsilon-2, while Epsilon-1 is the evil version, fought as a boss in one of the later stages of the game.