Zeta is a strange robot who ruled the city of Axiom Nexus. He randomly attacked Blackout when he appeared there, and made a "cliche exit" when Ynot also showed up. After he escaped, Blackout, showing an unusual amount of storyline awareness, said that they'd need to "wage a highly anticlimactic battle with him to make him let us out of Axiom Nexus". They then headed for the Axiom Nexus Central Tower, which was two weeks away on foot.
While they were heading there, Zeta sent his goons Dirge and Thrust to attack them, but they were defeated. When Zev Raregroove sent Archer as a gift for Blackout and Ynot, Zeta reappeared and blasted him. Archer responded by slashing at him and making him crash.
Ynot then ran over to Zeta's crash site, only to find it mysteriously empty. As it turned out, Zeta was bound by honour to leave the city after his defeat, and he roamed the universes for the millennia to come, seething.
During the Battle of Omega Supreme, Zeta finally found the one he believed responsible for his exile; Ynot. He attacked the Makuta, but was easily defeated and forced to withdraw.
When DiSalvatore rebelled against Ynot, Zeta struck again. After a brief battle with Xeno, Zeta finally confronted Ynot, who, after finding out why Zeta was so angry, blasted him with sufficient force to blow him through the fourth wall.