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For other uses of the term, see E-104 Epsilon (disambiguation).

E-104 Epsilon (E-104"イプシロン" E-104 "Ipushiron"?), or E104ε, is a character that appears in the Sonic the Hedgehog series. He was an animal-powered robot created by Dr. Eggman, and the fourth unit in the Doctor's E-100 Series. Epsilon, along with his "brothers", were created during the Chaos incident to serve as the Egg Carrier's elite crew. After failing his first mission, Epsilon was destroyed by E-102 Gamma.


E-104 Epsilon was a humanoid robot colored in orange and white. He possessed no neck, his head and torso coming together in an almost ellipsoid shape. His torso was orange with a wide and white vertical stribe down the middle, and possessed a head light with a hexagonal gray frame on the right side. He also had gray mufflers surrounding the pelvis area, and had the number "104" painted in white on the right of his large vertical stripe and the left side of his rear. His head meanwhile was small and platform-like with a yellow shade and green cylindrical eyes. He also had a Jet Booster hovering behind his neck.

Epsilon's shoulders were black vertical cylinders. Attached to each of them were Epsilon's arms, which were long and designed with two joints; each of Epsilon's forearms were designed as twin STINGER missile launchers. Originally though, his left arm held a black-gray blaster while his right arm had a tri-digited hand with two points of articulation on each digit. Also, Epsilon's upper arms were orange, while the parts between his upper arms and forearms were gray. Epsilon also possessed two long and inverted legs with five points of articulation and large, black feet with two sharp toes and roller wheels on the heels. The upper sections of his legs in particular were orange while the rest of them were gray, except from his calves, which were thick and orange.


E-104 Epsilon being discarded.

E-104 Epsilon was built by Dr. Eggman to be an elite member of the Egg Carrier's crew during the Chaos incident. Together with his brothers Gamma, Delta and Zeta, Epsilon was sent to look for Froggy. Epsilon, however, did not find the right frog. As punishment, Eggman banished him, along with the other E-100 units that had failed him, from the Egg Carrier. During his banishment, Epsilon received two missile launchers and a Jet Booster.

Gamma later found Epsilon inside a volcano in Red Mountain. There, the two robots fought a heated battle, which ended when Epsilon was destroyed. Afterward, the Robin powering Epsilon was freed.

Powers and abilities

After being banished from the Egg Carrier, Epsilon was equipped with twin STINGER missile launchers on the arms, which were useful for taking out moving air targets. He also acquired a Jet Booster that granted him the ability to hover in midair.


E-104 Epsilon is the third boss in E-102 Gamma's storyline in Sonic Adventure and Sonic Adventure DX: Director's Cut. He is fought with E-102 Gamma. To initiate the battle with Epsilon, approach Epsilon when reaching the end of Gamma's version of Red Mountain. The boss battle takes place in an enclosed area with Rings lying around.

Boss guide

Epsilon is a relatively simple boss, using the same attack patterns and movements as E-101 Beta and E-103 Delta. Keep in mind though that Epsilon can shoot missiles much faster than its predecessors. In gameplay, he will either stay in one place and shoot at the player with homing missiles, or fly using his Jet Booster. Using Gamma's Homing Missiles, the player can inflict damage on Epsilon and destroy his rockets.

If Gamma stands too far away, Epsilon continues to fire missiles, which will interfere with player's ability to target the robot. To quickly end the battle with Epsilon, get near him. When scoring a hit, wait just long enough for Epsilon to shake it off, then fire again. After landing five blows on Epsilon, this boss will be defeated.


Title Artist(s) Music Length
Heartless Colleague ...Boss: E-Series Targets Jun Senoue, Yoshitada Miya



Sonic Adventure Boss 14 - E-104 Epsilon



In other media

Archie Comics

Sonic X


  • Epsilon is the fifth letter of the Greek alphabet and E-104 Epsilon is the fifth E-100 robot made, the numerical descrepency from the model numbers is due to the fact E-100 Alpha, better known as ZERO, is still considered an E-series unit.
  • Although Epsilon's later weapons are visibly different from Beta and Delta's missile launchers, they function identically.
  • Despite his lock-on ability in his upgraded form, Epsilon visibly lacks a targetting sight like Gamma.
  • Although he no longer has a functional forearm due to his missile upgrade, a mirror reflection of Epsilon's original forearm still appears on his front skirt plate. This is due to the fact the reflection is an actual painted image within Epsilon's texture, which was repurposed from Gamma's textures.
  • His Jet Booster seems to let him fly for a short time, instead of hovering like Gamma's.



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