"Once my name was spoken in whispers and it brought dread to this land" — The Forgotten God, when awakened in his temple.
The Forgotten god is a deity who was once married to the Mother Goddess, and is the Final Boss of Overlord: Raising Hell.
History
The Forgotten God was married to the Mother Goddess. However, when she caught him cheating on her, she banished him to the Infernal Abyss and blocked all memory of him from the minds of mortals (anyone who tries to remember him quickly forgets). This is apparently "almost as bad as death" for a god, and he seems obsessed with making people remember him again.
Overlord: Raising Hell
Determined to escape the Abyss and begin a reign of terror, the Forgotten God opened several Abyss Gates across the Third Overlord's conquered lands, entrapping his subjects and condemning them to misery.
The Forgotten God, full with anger, is roaring.
Along with the suffering of the deceased, this would eventually enable him to enter the living realm and wreak havoc on all that is of the Mother Goddess' creation. He was stopped, though, by the Third Overlord, who sought to take the Abyss for himself. In the final confrontation against him, the Overlord burnt his body to ash.
In his final breath the Forgotten God destroyed the Infernal Abyss Gate, leaving the Overlord trapped. With the Forgotten God dead, though, the Wraiths under his command pledged loyalty to the Overlord, leaving him as the new Lord of the Abyss.
Note: The Forgotten God sweep attacks appear to deal a random amount of damage. Sometimes it does nothing, sometimes 1 bar of Health, and other times reducing the Overlord from full to 2/10 of hp (with fully upgraded Arcanium Armor). Arcanium Armor with at least 20-25% Health Regeneration is recommended if you are not familiar with his fight.
The Forgotten God's head.
Personality and Traits
The Forgotten God has a serpent-like form with many tusks, though wears a golden mask which completely covers his face.
He is incredibly vain and condescending, seeing all mortals as beneath him, including the Overlord, and regards the Mother Goddess with utmost contempt for punishing him, despite having brought her wrath upon himself.
The death of the Forgotten God at the hands of the Third Overlord.