Xi attacked three of the Freedom Fighters-Sonic the Hedgehog, Princess Sally, and Amy Rose-when they entered the territory of Egg-Boss Thunderbolt, to whom Xi had been lent. It pursued Sonic doggedly, only to run into his allies Mighty the Armadillo and Ray the Flying Squirrel. Ray flew Sonic out of Xi's reach, while Mighty swiftly dispatched the robot, much to the chagrin of the Soumerca Egg Army. (StH: #264)
- Xi was never formally introduced in the comics prior to Worlds Collide, but his fate was revealed in the (now defunct) Sonic Universe blogs.
Xi was never seen in the original continuity; in the post Super Genesis Wave universe it appears as a cat or simian-like variant of the usual E-100 design.