Kaernk

 The Kaernk''' is a water creature that is invisible to the naked eye, but can be found by the splashes it makes as it walks through the water. A number of them were delivered to Castle Brennenburg, where they were stored in deep wells where Tampter, an ingredient for a life-extending potion, could be extracted safely from the creature's saliva. The Kaernk's blood is yellow, a discovery made by smashing a heavy object, such as a crate against its skull. However, because of its invisibility, not much else is known. It is believed that Kaernks cannot survive on land.