Allelujah Haptism spent his childhood as an orphan in the Human Reform League as a Super Soldier experimental subject, designated "E-57". While generally gentle and rational compared to the other Gundam Meisters, he has a harsher, unstable, and outright sadistic alter ego, named Hallelujah inside him, which was the result of his distorted Quantum brainwaves. His main rival in combat is another subject of the Super Soldier program, the HRL pilot Soma Peries who shares a mysterious connection with him.
He is the pilot of Gundam Kyrios, and later, the Arios Gundam, both of which specialize in high mobility and are able to transform into fighter jets. Allelujah is imprisoned during the four year time-skip between both seasons, but he ends up being rescued by his companions after the other three Meisters reunite.