You have heard of the Trolls

Troll (Norwegian and Swedish), trolde (Danish) is a designation for several types of human-like supernatural beings in Scandinavian folklore. They are mentioned in the Edda (1220) as a monster with many heads. Later, trolls became characters in fairy tales, legends and ballads. They play a main part in many of the fairy tales from Asbjørnsen and Moes collections of Norwegian tales (1844). Trolls may be compared to many supernatural beings in other cultures, for instance the Cyclopes of Homer's Odyssey. In Swedish, such beings are often termed 'jätte' (giant), a word related to the Norse 'jotun'. The origins of the word troll is uncertain.

Trolls are described in many ways in Scandinavian folk literature, but they are often portrayed as stupid, and slow to act. In fairy tales and legends about trolls, the plot is often that a human with courage and presence of mind can outwit a troll. Sometimes saints' legends involve a holy man tricking an enormous troll to build a church. Trolls come in many different shapes and forms, and are generally not fair to behold, as they can have as many as nine heads. Trolls live throughout the land. They dwell in mountains, under bridges, and at the bottom of lakes. Trolls who live in the mountains may be rich and, hoarding mounds of gold and silver in their cliff dwellings. Dovregubben, a troll king, lives inside the Dovre Mountains with his court, as described in detail in Ibsen's Peer Gynt.