Cathaluss is one of the three perfect beings called the Angelblood created by the Greek Gods to rule their realms when they ascended beyond physical form: Cathaluss (to maintain order in Hell), Trionus (to rule the immortal celestial realm) and Gaea (intended to rule the mortal realm).
Cathaluss is opposed by Darkness, the demon lord who is currently seeking the Mask of Torment, Hades Crown in order to seize control of Hell for himself.
Saroth also challenged Cathaluss in Hell as part of an attempt to carve out a place for himself in hell and earn respect. It was arguably successful as he survived (barely) and attracted Darkness's interested attentions.
As an Angelblood with a body forged by the Greek gods, Cathaluss is invulnerable to harm. He is also extremely fast and strong, even by superhuman standards. Cathaluss can fly and has psionic abilities and cosmic powers. His cosmic energy has a lingering effect upon those unfortunate enough to experience it - Saroth likened it to his body being killed from the core.