The Sverdhvalur, which translates as swordwhale, is another of the illhveli (evil whales) lurking off the coasts of Iceland.
Like all other illhveli, its meat is uneatable, poisoning those who dare try it.
Its most distinctive feature is the sharp bony fin growing out of its back.
After reaching maturity, sverdhvalurs are as large as a sperm whale, and like this whale they have a large mouth set with vicious teeth.
The blue whale (Steypireyður in Icelandic) is its mortal enemy. Most of those who have seen a sverdhvalur, described it as brown in color with a sleek skin that shines when touched by light. However, when far from the coast, sightings of this monster contradict this accounts, describing it as grey with a top that at times shines yellow.
The sverdhvalur is a fast swimmer. They are not solitary animal, and adults are often accompanied by a smaller whale, thought to be their offspring, swimming under its pectoral fin and feeding on its scraps.
They use their bladed dorsal fin as a weapon, swimming underneath other whales to cut their bellies open with crisscross slashes. Whales will beach themselves rather than suffer a sverdhvalur’s attack.
This evil whales are not only vicious but also wasteful eaters, choosing to eat only the tongue of their prey (generally cetaceans or barbed whales) and leaving the rest to rot.
They treat boats in the same way as they attack other whales, punching holes through hulls, slicing cleanly through if the boat is small enough, with their dorsal fin. If any sailor falls in the water, they will eat them.
Encounters with larger vessels are more harmful for the sverdhvalur. Old records tell of a trading ship sailing from eastern Iceland to Copenhagen. Midway, the vessel stopped in the middle of a large pod of whales after a sudden and strong tug coming from below. When the ship moored in Copenhagen, the large tusk of a sverdhvalur fin was found sticking out of the hull.
-Árnason, J.; Powell, G. E. J. and Magnússon, E. trans. (1866) Icelandic Legends, Second Series. Longmans, Green, and Co., London.
-Davidsson, O. (1900) The Folk-lore of Icelandic Fishes. The Scottish Review, October, pp. 312-332.