Magog was the offspring of the fallen angel Avengelyne and the demon Kyle Wagner. Wagner was chosen because his blood matched hers perfectly as usually angel and demon blood do not mix well. At his birth, he instantly tried to kill his mother. Even with the help of the powerful Angel of Death Passover they could only force him to retreat. He may be the most powerful demon to ever exist.
When the angel Micah began his rebellion against God and the Dragon, Magog joined him as Death and was charged with leading the lost souls of Purgatory against the angel and demons at the final battle of Armageddon - Megiddo. On the field of battle, he was met by Devlin Trask who attempted to kill Magog by using his demonic powers, which were unstable. His sacrifice did not work, but revealed to Avengelyne his true identity.
After nearly defeating his mother, who had her full angelic powers, Avengelyne decided to use her power to take Magog back into her being, thus removing him from existence.