In End of The World, Magus is mentioned as the first Phase retrieved by the Salvage Project created by Jyotaro Amagi and Jun Bansyoya. Following the disastrous test of the Epitaph User program, Magus was the only Phase that was able to be captured and sealed by CC Corp before it could escape into the system.
Magus is the Avatar controlled by Kuhn, who always refers to it as "My Magus". Magus is the first Avatar encountered by Haseo after Kuhn uses it to save Haseo and Atoli from an "Anna"-type AIDA. Haseo soon learns how to control his own Avatar, but when he begins using it recklessly in the Arena, Kuhn realizes he has to teach Haseo a lesson. He uses Magus to fight against Haseo's Skeith in an arena match. As Kuhn suspected, Haseo loses control of Skeith who rips Magus into pieces. Luckily Kuhn had prepared for this and used his special "Propagation" ability ahead of time, which gives him the power to duplicate data such as his Avatar. Though the Magus that Skeith had destroyed had only been a clone, Haseo learned how dangerous Avatars could really be, learning the lesson Kuhn had wanted to teach him.
After Haseo is attacked by an AIDA-controlled Bordeaux, Kuhn appears and summons Avatar Magus to cleanse the AIDA from her PC. He tells Haseo that he controls Magus because he is an Epitaph User. Haseo realizes that he has a similar Epitaph inside of his character and swears to unlock it.
- Energy Shot: Magus will spray energy blasts out of his two hands towards his opponent.
- Leaf Shield: Magus creates a shield with six leaves, repelling and damaging any that attacks close up. Shoot to destroy. Upon destruction of the shield, Magus will be left stunned.
- Flash of Green: Magus charges up, then fires multiple laser beams at once which move up and down.
- Unforgiving Bud: Magus releases 10 seed-like time bombs across the screen that will then encircle Skeith. Slash to destroy as many as possible.
- Data Drain: Magus has the Data Drain ability, but will not use it in the fight against Skeith.
- Magus is the only Avatar that will not use Data Drain during its fight, most likely due to the fact that Kuhn was not attempting to destroy Haseo, but Magus uses its Data Drain when he fights against the AIDA Anna that Endrance made when Haseo first met him in Indieglut Lugh.
- Magus's G.U. theme song is called "The Differences Between People."
- In the G.U. Novels, Kuhn uses the skill, "Flash of Green" to data drain the AIDA in Indieglut Lugh.