Betheal Gavarre

Betheal Gavarre, also known as Belial was originally an inquisitor in the medieval church called Betheal. However, he eventually comes to preside over the case of the possessed Vascar de Guillon, who has been captured. Temozarela, who is inside Vascar's body, influences Betheal's adoptive son, Matthew, to slaughter one of the women at the monastery where he and Betheal are staying. Betheal, on hearing his son confess this, becomes enraged and strangles him, not fully realizing Temozarela's influence within him.

Later, he realizes that Temozarela had orchestrated this to shatter Betheal's faith and had succeeded. In remorse and in rage, Betheal sacrifices himself to become the devil Belial by condemning his faith and renouncing God. However, instead of joining Temozarela, Betheal uses his new power to fight against him, eventually imprisoning himself, and Temozarela in the Domas Porada to keep him from the world. Later, after the Domas Porada is opened, he offers a deal to the imprisoned Ivan Isaacs, which the insane priest agrees to, leaving Belial's mark of a cross in a circle branded on his forehead.

Trivia

 * When Belial confronts Achmode, the fallen angel asks Belial if he remembers what life in Heaven was like. Belial proclaims that his origins are not that of Achmode's and his kin. The fallen angel counter replies by referring to the latter as the "First Angel."
 * In volume 13th during a flashback of Netraphim's fall from grace, Temozaraela tells Netraphim how Abaddon turned his back on God and left Heaven. He is also called the "First Son of Light" by the angel. This could mean that Abaddon is the entity that Betheal sold his soul to in order to become Belial.
 * The "First Angel" could also be Lucifer who was the first angel created by God in Christianity. If so, this could be why Belial is referred to as the Devil by every character in the manhwa.