When Doctor Robotnik absorbed the power of the Chaos Emeralds and became an omnipotent God, he resurrected several villains in an attempt to destroy Sonic. One such villain was Plasma but, despite all of Robotnik's power, the former dictator felt the need to also resurrect Abacus to control Plasma once more. Abacus was killed by his own monster when Sonic knocked Commander Brutus into Plasma, causing a chain reaction that destroyed all the villains.
During Sonic the Hedgehog's fall from grace, Sonic was left wondering who was impersonating him in an attempt to remove all confidence in him. As he pursued a Mega Mack missile heading straight for the Green Hill Zone, Sonic brought up a long list of potential suspects with the Kintobor Computer, Abacus being a last resort with no better ideas.
Although Abacus appears to be a shy villain who prefers his creations to do the dirty work, Abacus seemed to be initially talkative when confronting the Freedom Fighters. He took a backseat during the battle, attempting to keep unnoticed. Abacus has a slight inferiority complex, declaring his name even though he believed nobody would be interested. Despite this, he took offence when Sonic failed to mention his name after his resurrection.
- Arnem Abacus was an idea of Richard Elson's that was tweaked by Nigel Kitching so that it would work in a story.