In the years before the advent of arcanotechnology and dimensional fatigue events, teratology was the study of abnormalities and biological deformations. In the wake of the second renaissance, it became the study of exomorphs, extradimensional entities, and most prominently, teratomorphs, more commonly and vulgarly known as kaiju.
To purify the water from a certain river the monks have carved a section of the river that goes over a stone bed. Through holy carvings of gods, godesses, and holy symbols and then the river flowing over them, it purifies the water making it safe for drinking and/or makes it holy water. For rivers that do not have natural rock bottoms, large smooth stones can be carved and added to the water to fully cover the bottom.