The Kraken is a legendary sea monster of giant size that is said to exist off the coasts of Norway and Greenland. It was first mentioned in an old Icelandic saga called Örvar-Oddr, which was written in the 13th century AD; as the main characters of the saga sailed across the sea of Greenland, they encountered two monsters, the Lyngbakr and the Hafgufa. The Hafgufa is linked to the kraken.
The unknown author of a scientific paper which was also published in the 13th century described the behaviour and characteristics of the two monsters after returning from a trip to Greenland. The author mentioned the monsters were not capable of reproducing as only two of them were ever seen. The famous botanist and zoologist Carolus Linnaeus included the kraken in his taxonomy book Systema Naturae in 1735, and classified it as a cephalopod; the entry was removed from later editions of the book.
Originally, kraken were considered to be similar to giant crabs, having similar characteristics to giant whales as well. However, in later versions, kraken have been described as giant creatures resembling an octopus. The suckers on their tentacles have spikes.