For a futuristic grim gory setting. Probably powered by some kind of dilithium battery or something similarly awesome. Anyways, basicly a big drill sticking up from a hilt that you primarily use for skewering enemies painfully and drilling through armor.
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.