Long before this middle age of Wizardry, the people of the Elder days shared this world with Elves, Dwarves, the Fey and the Fell. The depredations and destruction wrought by demon kind and other Fell creatures made life a hazard and a tenuous thing.
Shamans and Wizards, Priests and Witches, Seers and Seeresses along with anyone else with even a hint of magic were called to a great meeting. It was decided to attempt a Banishment of all the Fell creatures from the Elder days. A great labor was made to construct the massive spell. There under a full moon at a most auspicious moment it was initiated and released.