Katan used to be a lowly angel, who was to die and give up their souls, then become mindless puppets. But Rosiel gave Katan a body, practically giving birth to him. Thus would be the reason why Katan became to loyal to him, loving Rosiel much like a father. Katan is the man that gives all the children the Angel Sanctuary "game" to collect energy to awaken Rosiel from the Earth. Katan is to help with the awakening of Alexiel.