The Lost River - James Farrell - Bog

When the Drawers of Vond, the magical life of the world, become corrupted, there is no recourse save to the Cardinal; and when he too is corrupt, the only recourse is to the Pope. And he, he is in another world, accessible only by an enchanted Window, and that Window is held shut by the Cardinal. Then the Cardinal and the Drawers committed a great sin, and to increase their power to magic, they diverted the Lost River.