The Flood Priest's Garden

From the description:

In a garden, once used as a holy site by members of the Order of the Green Mice, sits a pond and a large apple tree, as well as a dark secret. From the depths of the pond a catfish has seduced a wizened mouse mage into doing his dark bidding. High atop his tower in the apple tree, the Flood Priest uses magic from the deep to flood all of the garden and turn it into the realm of the catfish. Strange creatures have emerged from the water and the mice of Terra-Potta are fleeing the garden in droves. There are some who think If proper alliances are made, the catfish can be taken down or the flood priest can be stopped. Rumors have been stirring that the end is near, and all will soon become the Flood Priest’s Garden.