The whale remains floating at the surface for long periods, so its back becomes covered with sand. Approaching sailors, thinking the whale to be an island, land there and build a fire to cook their food. After a time the heat penetrates the whale's thick skin, and it dives to cool itself. The ship is dragged down with it and the sailors drown.

When the whale is hungry it opens its mouth and emits a sweet odor, which attracts small fish. The fish swim into the whale's mouth, which closes on them.

The pyster is the sperm whale (Physeter macrocephalus); it is found in some medieval encyclopedias. It is described as being like a large pillar that is taller than a ship's sails, and to produce a deluge of water.

The whale who deceives sailors and drags them down to their deaths signifies the devil, who deceives those he drags down to hell. Those of weak faith who give in to the sweet odor of worldly desires will be swallowed up by the devil.

Hildegard von Bingen says: "A person who is delirious should frequently eat a sufficient amount of this meat, with only bread in addition, and he will recover his senses. ... One who suddenly becomes weak in his heart should pulverize whale’s heart and drink it in water, and he will be better. ... One who eats some of a whale’s liver purges the inside of his stomach. It takes away all interior dirt from him, just as the best purgative. In any house or place where airy spirits are accustomed to produce their mockeries, burn the liver of this fish over live coals, and they will go away. They will not be able to remain in that place because of the powerful odor. ... Also, make a knife handle from the bone of this fish. Hold that handle in your hand until it warms up. There is no pain in your hand or arm that will not cease. ... Make shoes from whale skin and put them on. You will have healthy feet and legs. Also, make a belt from this skin. Gird yourself with it against your bare skin. Various infirmities will flee from you, and it will make you strong." (Throop translation)