From Sonic - NeoWiki

History

Omega, also known as E-123 Omega, is a robot who first appeared in Sonic Heroes. Omega is the last of Dr. Eggman's E-100 robots, and was designed to control Shadow the Hedgehog. Eggman traps Shadow and Omega in a stasis pod until Shadow is released by Rouge the Bat. Omega is furious and teams up with Shadow and Rouge to get revenge on Eggman. In Shadow the Hedgehog Omega appeared as a partner to assist Shadow.