|This character exists primarily or exclusively within the Sonic Underground continuity.|
Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
When Knuckles was about to leave the Floating Island to help Sonic, Manic and Sonia stop Dr. Robotnik's Chaos Emerald-powered Fortress of Altitude, Athair appeared before Knuckles in a vision and warned him not to leave the Floating Island, as doing so would destroy all of Mobius. As Knuckles asked him if there was a way so that he could both protect Mobius and help his friends, Athair remarked that it was possible to change the future this way, but noted cryptically that it depended on Knuckles' decision, before disappearing.
Later on, Knuckles, Sonic, Manic and Sonia came to Athair, seeking his help on how to contain the Chaos Energies from a lost broken Chaos Emerald, which threaten to destroy the planet. Having already seen and sensed the events transpiring, Athair provided Knuckles and his friends with a canister to contain the broken Chaos Emerald and its energies. However, he revealed firmly that to save Mobius, they had to make an alliance with Robotnik.
After Knuckles and his friends succeeded in containing the broken Chaos Emerald by allying with Robotnik as Athair predicted, they returned to give him the Chaos Emerald fragments for safekeeping. Athair, however, declined, since it was Knuckles who was meant to guard these fragments on the Floating Island. Sonia then though Knuckles would join the resistance now, but Athair told her that Knuckles' duties were to the Floating Island, like Sonia and her siblings' duties were to the resistance.
Athair is very wise, and never wrong. He is rather serious and breaks no argument when he makes a decision. However, he possess a little sense of humor and thinks well of his great-grandson.
- Athair is the only character to originate from the Archie Comics and then be incorporated into the storyline of a cartoon series.