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. E-102 hunts down his younger sibling in Windy Valley, and after a fierce exchange of missiles in the boss fight, Delta is destroyed.
E-103 Delta during the boss fight.