Erū Ilúvatar, also known as the One, was the supreme being of Eä He was the single omniscient, omnipotent, and omnibenevolent creator of existence. He had been existing eternally in the Timeless Halls and possessed the Flame Imperishable in his spirit, which has the power to kindle existence from nothingness.
Though the Ainur attempted to shape and govern Eä according to Erū's general will (which they understood imperfectly), he gifted his creations with the will to ultimately do as they pleased, and intervened directly in the affairs of Eä on only extremely rare occasions.