Huldra

One of the most darkest creatures of Scandinavian folklore is the Huldra. They belong to the Huldrfolk species of creatures. Both males and females are said to be guardians of the forests and mountains. They live in secret and hide away. The female Huldra appear like seductive beautiful women with flowing hair but they have features that are not human. They're said to have tails. If they turn their backs, they resemble trees with hollows. Stories and legends about people encountering the Huldra are a bit nasty. For example, Huldra can manifest in rain and storms, while seducing men in order to kill them. They can look like dairymaids but more striking and with enchanting beauty that men fall in love instantly, only to become victims. Women have also come under the spell of the Huldrefolk too. In some stories, the Huldrefolk are keen on human blood and will kidnap people, or send them to a darker place. It's been said that if a human marries a Huldrefolk, then the creatures lose their tails and become human themselves, only they still keep their magical abilities and connection to the forests and caves. They're also believed to steal human babies and replace them with changelings. Apart from the scary stories, not all are wicked like that. Some tales of Huldra and Hulder men are also kind and helpful. They have to be respected as one respects others. As the old saying goes, treat others the way you would want to be treated yourself. The same applies to Hundrefolk. If you respect them, they'll do no harm.
Howls ^^