Sorcerers from all eras were drawn to a power in a specific time, the power of an ancient book known as the Word of God. Merlin feared this power and imprisoned all the sorcerers who sought the book in a magic cell which over time had a corrosive effect that caused the imprisoned to merge into one being known as The Forgotten.
The Forgotten would break free and seek revenge against Merlin and attempt to obtain the Word of God until they were stopped by the Sorcerers Supreme.