One of the many creatures of Swedish folklore was the 'hulder' (or most often 'skogsrå' in Swedish [one of many names]).
The hulder was a female spirit and caretaker of the woods, who relatively often came in contact with humankind. She was often seen as a seductress, with an unending appetite for men, and if you were blessed or cursed with becoming her lover, you could expect to have good hunting for the rest of your days, as long as you stayed faithful to her and didn't shoot her riding elks. The less obviously positive side of the coin was that your thoughts would remain occupied with thinking of the hulder and you would seem laconic and introverted to your fellow human beings.
The hulder was sometimes pictured as having a hollow back, sometimes as having a tail and sometimes as having hooves or animal feet of other kinds. All these descriptions, be they of her physical form, temper, habits or role, varied depending on where you were geographically, but her role as a seductress seems to have been fairly constant across the map, even if this needn't always have been the case. In this, she resembles many (some would say most) other female beings from folklore and mythology, be they succubi, sirens or others, as their femininity is reason enough to award them the role of false, vicious femmes fatales, using men for sport and their own nefarious goals. Interestingly, this role doesn't seem to be that old when one considers the skogsrå/hulder. The name might have its origin in the Norse character 'Huld', who was a woman able to use and practice seiðr/sejd (a type of sorcery). Though villainous in some sources, the "temptress" side of her role seems of newer date; possibly under Christian influence, as the hulder of folklore has also been described as the daughter of the Judeo-christian figure Lilith.
The hulder belonged to the category of beings known as 'rådare'. These are guardian spirits of the trees, rocks, hills and waterways and include diverse beings such as nymphs and gnomes. In fact, some of the inspiration for Santa Claus comes from the Scandinavian being known as the 'tomte', the guardian of the estate or farmstead, who is a rådare.