E-105 Zeta is one of the E-100 boss robots that E-102 Gamma must fight in Sonic Adventure. When it was first built, it looked identical to the other E-100 units. After failing its mission to capture Froggy, Dr. Eggman punished Zeta by having it taken apart and installed within the Egg Carrier's engine room. When Gamma returned to the Egg Carrier after destroying Delta and Epsilon, it found that Zeta had been rebuilt as part of the ship's engine. It appeared to be a massive dome-shaped turret covered with cannons that continuously launched missiles at Gamma as he was carried around on a turntable surrounding Zeta. Gamma was able to defeat Zeta by taking out all of its guns. Without any weapons and unable to move, Zeta malfunctioned and exploded.