Neroda's Air

Demons can't breathe underwater. But in this case, how to explore the seabed? The non-native Seer struggled for a long time to solve this problem. He studied different ways, and runes came to the aid of the researcher.
 
He applied them to special cylinders, so that they began to hold a huge amount of air. With the help of a system of tubes and valves, the carrier of the "Neroda air" could breathe on the seabed.
 
But such a system was very expensive, so only one was made. After Nerod's death, no one wanted to continue his work and study the ocean floor, so the "Nerod air" became a point of pride for collectors.