Keystone Fragment

The Keystone Fragment, commonly referred to as the "Halo", is a special artifact that grants god-like powers when it is worn. It serves a large role in the universe, especially throughout Madness Combat episodes 10-11. The person that it is seen most with is Jebediah Christoff, where the Halo is the source of all his deadly powers. Other than Jebus, Tricky, Hank, and the Auditor have wielded it, and have demonstrated some of its powers.

Depending on the wearer, the Keystone Fragment grants surreal powers in which the user can be near unstoppable. It operates Dissonant Reality (Dissonance for short). Dissonance is the power Jebus uses that can disintegrate enemies, which is why this artifact is considered to be dangerous.

In Episode 1.5 of Madness: Project Nexus (Classic), Jebus was the first to use it and also the first to steal it in level E - Vaults. It made him stronger and faster, with the powers of Dissonance in his hands. He was even able to levitate. Using the artifact to his advantage, he was able to clear out the building and kill Phobos. He then became the owner for more than 20 years, eventually losing it to the Auditor after dying in Madness Combat 8.

The Keystone Fragment became into the Auditor's possession. This granted him enhanced strength, though Dissonance wasn't showcased in his attacks. He became able to absorb the dead bodies of others, and convert the energy into a large sword. However, he accidentally absorbed Tricky's dead body in the process. Because of his inept mistake, Tricky became the new owner of the Halo. That made him the main antagonist of Madness Combat 11.

At the end of MADNESS: Project Nexus's Story Mode, Jebus gets blown off the Science Tower by Hank and loses his Halo. The Halo then fades into a black color, implying it being inactive.