E-118 Tau is an E-100 Series robot.
Tau was sent to retrieve the lost Chaos Emerald in the Thunder Plains Zone. The Freedom Fighters, having teamed up with the native Wolf Pack, had managed to distract it from its set course thanks to the bravery of Sonic the Hedgehog and Lupe the Wolf. Using one of Dr. Ellidy's Sling Rings, Sonic had managed to lure it into the most active part of the ongoing storm before flinging back to safety, narrowly escaping the stray lightning-bolt which struck Tau dead. (StH: #277)
- Tau was never formally introduced in the Pre-Super Genesis Wave Timeline, but its fate in that universe was revealed in the (now defunct) Sonic Universe blogs.
- The general design of Tau is modeled after the traditional depiction of a flying saucer.