
Jack Frost, a popular frozen persona during wintertime.
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Jack Frost is believed to have come from Germanic folklore, and was very popular with the Anglo-Saxon and Norse during winter. The crystal patterns of frost found early in the morning on the windows were said to be from Jack Frost. He is described as being the persona of cold winter and is elfish. He is also a variant of Father Winter. In a Finnish epic he comes from his father, Blast.

A transformed Berserkr after a battle.
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Berserkir (plural), Berserkr (singular)
Berserkir are from Norse lore and their name, directly translated, means “men in a bear shirt.” Their name is also the foundation of the english word berserk, meaning uncontrolled chaotic behavior.
Werewolves at Will
Berserkir were destruction-loving warriors who often wore bear or wolf skins over their armor. The animal skins were thought to give the berserkir demonic powers and also giving them the ability to transform into either a bear or a wolf. Many Norse legends of werewolves involve berserkir and their ability to transform at will.
Berserkir also had the ability to work each other up into frenzies, where they could gain demonic possession. This possession was said to make them invulnerable to fire and swords. They could, however, be destroyed by beating them with a club. After they would be done battling they would become extremely exhausted.
Facing the Berserkr
In Norway, berserkir would often challenge local farmers to fight. If the farmer declined or was killed, he had to give all of his property to the Berserkr. If they knew someone was having a gathering where a lot of food was involved, very often Berserkir would invite themselves over and make themselves at home. If anyone had a problem with them, they would split open their skull or snap their backbone. As Christianity made its way through Europe, Berserkir became less popular.