Archdemon
Some random dude on the Internet
When the universe was created and the first two gods emerged, there was a third. This third being was the one to corrupt Gaia, who killed her own husband by using her own son to do it. Down the path of time, this "God" had corrupted the titans as well but they were foolish and attacked him forcing him to ally with their children. The titans were defeated and their offspring took control, but they feared their so called ally. They knew they couldn't defeat him so they locked him away, not in tarturus, but in the far corner of the deep, dark void. They created a powerful beings to watch over him to make sure that he'll never escape. While he never truly escaped he slipped past his guard and arrived in the mortal realm where he created his own offspring, And soon this Demigod will be the key to his cage. The first Evil will be free and he'll make sure that all will be corrupted.