bagiennik

Bagiennik was the name of the water demons in Slavic mythology. They are related to the Bannik spirit. They were subject to Wąda, lady of lakes and shallow currents, also known as Queen of the Submarine Meadows.

The Bagienniks lived in the depths of lakes and rivers. They were able to emit an oily substance from the nostrils, which were located between the nose or the forehead. This substance was so hot that it burned victims, but it was also said to cure deep wounds, indigestion, heart disease and even infertility.

The presence of the bagienniks could be detected by the bubbles on the surface of the water, or by its darker and muddy color.

wiki