E-104 Epsilon is one of Dr. Eggman's E-100 models that appeared in Sonic Adventure. Its framework was the same as its batch brothers, though it could be identified by its orange paint job. Like E-103 before it, E-104 had a cannon on both arms, though these were chunkier and could fire more missiles in quick succession.
Epsilon was assigned to track down the mutant amphibian "Froggy", which had swallowed a Chaos Emerald and a portion of the liquid monster called "Chaos". Epsilon failed its mission and was banished to Angel Island, entombed inside the island's volcano. After E-102 Gamma abandoned Dr. Eggman and began hunting down the other E-100's, it found Epsilon inside Red Mountain and the two robots fought. Epsilon was destroyed and the animal inside its body was released.