E-103 δ, commonly known as Delta, is an Eggman robot from the E-100 Series, appearing in Sonic Adventure. Delta was one of the E-100 series robots designed by Dr. Eggman. A blue android who can fly using his Jet Booster plate, Delta functions as a boss for E-102 γ at the end of Windy Valley.
Delta is first seen aboard the Egg Carrier in Gamma's story, when Dr. Robotnik gathers the E-100 Series in the main hall to send them out on a mission: the capture and retrieval of Froggy. Eggman requires Chaos's tail, which has attached itself to the amphibian, in order to restore the God of Destruction to full fighting fitness. Gamma is dispatched to Emerald Coast while Delta, Epsilon, and Zeta go to search elsewhere.
Gamma is the last one to return to the Carrier - and the one who actually caught Froggy. Delta has brought back a blue and red frog, and the Doctor is rather unforgiving of failure, banishing Delta, Epsilon, and Zeta with "All you worthless hunks of junk, begone!". Delta exchanges an unreadable look with Gamma as he is teleported away in a cyan beam of light.
E-103 is next encountered only when Gamma arrives to kill him. Whereas Delta was prior equipped with an identical gun-and-hand configuration to Gamma, he now sports a pair of missile launchers identical to those formerly wielded by E-101 Beta. Delta fights identically to Beta, employing his Jet Booster to move around the arena and pausing to fire homing missiles at Gamma. Compared to his predecessor, Delta is more durable and is faster to shoot; nonetheless, he proves no match for Gamma and is destroyed.
E-103 Delta during the boss fight.