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Sonic Wiki Zone
Sonic Wiki Zone

My frog is the right one!

— E-104 Epsilon, Sonic Adventure

E-104 (E-104 Ī 104?), codenamed ε or Epsilon (イプシロン Ipushiron?), is a character that appears in the Sonic the Hedgehog series. He was the fourth E-100 Series robot created by Dr. Eggman during the Chaos incident to aid in the destruction of Station Square.[1] Tragically, however, after a mission failure, Epsilon was remodeled and banished to the Red Mountain, where he was destroyed by E-102 Gamma.[2]


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 stripe 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.


Sonic Adventure[]

Dolphin 2015-10-14 18-43-39-618

Epsilon being discarded, from Sonic Adventure DX: Director's Cut.

In Sonic Adventure, its enhanced port Sonic Adventure DX: Director's Cut, and the 2010 remaster, Epsilon was created as the fourth unit in the E-100 Series of shooting robots in order to aid Dr. Eggman in his agenda to destroy Station Square and build Robotnikland on its ruins.[1] At some point, E-104 was able to become part of the Egg Carrier's crew, alongside E-102 Gamma, E-103 Delta, and E-105 Zeta. There, Robotnik tasked them to retrieve Froggy, who had swallowed a Chaos Emerald. However, Epsilon failed to locate the correct frog, and the doctor remodeled him, Delta and Zeta. Nonetheless, they were all banished from the Egg Carrier afterwards.[2]

It was later revealed that Epsilon ended up deep in the Red Mountain.[2] Gamma later tracked Epsilon down, intending to "rescue" him by destroying him, thus releasing the Animal trapped inside him. The two battled, and Gamma emerged victorious. Delta was destroyed, and the Robin inside of him was freed.

Powers and abilities[]

As part of the E-Series, Epsilon was a very advanced robot that was developed to advance weaponry.[3] After being remodeled, he 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, its enhanced port Sonic Adventure DX: Director's Cut, and the 2010 remaster. In Adventure Mode and Trial Mode, he is fought at the end of Red Mountain. He is only encountered with Gamma.

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) Length Music track
"Heartless Colleague ...Boss: E-Series Targets" Jun Senoue, Yoshitada Miya 1:25



Sonic Adventure Boss 14 - E-104 Epsilon

In other media[]

Archie Comics[]

Sonic X[]


  • 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 targeting 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.






  1. 1.0 1.1 "All Star Cast". Sonic Adventure Tokyo International Forum Unveiling Booklet. 22 August 1998. p. 9.
  2. 2.0 2.1 2.2 "E-102"γ"" (in Japanese). ソニックアドベンチャー オペレーションガイド. SoftBank. January 1999. p. 122. ISBN 978-4757203006.
  3. "Dr. Eggman in... My Greatest Invention". Sonic the Hedgehog: Rival Edition. Tomy. 2017.

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