E-103 Delta (δ) (デルタ,Deruta?) is the third of the E-100 Series robots constructed by Dr. Eggman. He appeared in Sonic Adventure, in which he plays a minor role in E-102 Gamma's story as a boss. He resembles the other E-Series robots, except that he is silver and blue in color. Delta stands 7'1" (2.15900 cm) and weighs 1819 lbs (825.084521 kg). He has the dual rocket launchers like Beta, but in addition it has a jetpack built into itself for short range flight. Delta also appears in Sonic X.
Along with his brother E-Series robots (E-102 Gamma, E-104 Epsilon, and E-105 Zeta), Delta was sent by Doctor Eggman to retrieve Froggy, who had swallowed a Chaos Emerald. When Delta failed to locate the correct frog, Eggman banished him from the Egg Carrier along with Epsilon. He stares at Gamma as he is teleported away, but it is unknown whether any feelings were stirred in the robots.
It is later revealed that he was abandoned at the Windy Valley. Gamma later tracked Delta down, intending to "rescue" Delta by destroying him, thus releasing the animal trapped inside him. The two brothers battled, and Gamma emerged victorious. Delta was destroyed and the animal inside him was freed.
At first, Delta is a clone of Gamma (except for the color), with just one cannon arm and a hand. After being discarded by Eggman, he inherits E-101 Beta's twin missile launchers and jet booster.
The animal inside Delta was a parrot. After he was banished to the Windy Valley by Eggman, Delta lived the remainder of his life there until being destroyed by his brother E-102 Gamma.
Delta has a Jet Booster, twin missile launchers and a target locater.
After Delta fails his mission and is banished to Windy Valley, he takes on the same design as the unmodified E-101 Beta, just painted with a blue color scheme, along with his number 103 on his side.
It can be assumed that Beta's discarded rocket arms were added to Delta.
If you hack into the games texture files, it is very likely that you can play as E-103 Delta before he was banished from the Egg Carrier.
His Jet Booster seems to let him fly for a short amount of time, instead of hovering like Gamma's.
There is a glitch where right before the boss fight, if the player was to jump of some high elevation and fly to the left, Gamma will land on a rock sticking out of the mountain, allowing him to "snipe" Delta.