Well, this certainly looks like a K’tonian artifact but if you notice the grooves on the bottom, that means that this was actually made on a Jiyong potters wheel as an imitation of the K’tonian style of pottery. This is a replica, albeit a 700 year old, very good replica. I do happen to know a buyer who would be willing to pay you for it.
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.