Disclaimer: you stopped here because you're searching for the gun manufacturer, sorry to disappoint but BOY have you landed in the wrong space. You've probably already figured out I'm not discussing the virtues and drawbacks of a gas-piston rifle and wandered off to HuldraArms.com. If you're still here, feel free to hang out and discover your gun is named for a hot female...who occasionally becomes a (literal) man-eating monster.
Also, while researching today's creature I found this: Huldra And Victim creation app. It's horrifyingly wonderful.
It's possible I wasted some time playing with online doll versions of pretty woodland people-ish entities...who eat their victims (presumably after the sex part, like a Norse Preying Mantis without the extra limbs). I sort of wish I could get a couple made for the family members who have a doll-phobia, but that's another story.
The Huldra (or Hulder: I'll use them interchangeably here because the terms aren't linguistically different in meaning) is a fascinating figure in Scandinavian mythology whose story and attributes changed as Christianity spread throughout the area. She is both beautiful and monstrous, naked and clothed, helpful and vengeful, compliant and deadly: all depending on how she's treated.
In the Pagan era myths, she is consistently described as a beautiful wild woman of the forest, who has an animal tail. In Norway the tail is always a cow's: in southern Sweden it could be a cow's or fox's. The further north you are, the more likely she has either a hollow back or a back covered in tree bark. Regardless, there is always something just a bit animal or forest about her.
In the earliest myths, the Hulder was often a seductive woodland fairy nymph, and was usually recognizable as something other than a human woman only because of the tail. Dealing with the Hulder is somewhat similar to the Irish Celtic ideals of dealing with Fairies: politeness is paramount, satisfaction is rewarded. It's also interesting to point out the Hulder myths don't have a lot of mortal women involved (in general, the Hulder appear to be a temptation to men alone, much like a Succubus, only without the demonic aspects).
There is a male version, the Huldercarl, who acts in a similar manner as the Hulder only toward women: the gender specificity implies both the Hulder and Huldercarl are examples of man and woman dealing with the dangers and bounty of the wild.
Legend has it, a man (or woman) who is kind, polite, and sexually satisfying is rewarded by the Hulder/Huldercarl. However, every power comes with a price. The old myths of Hulder include her ability and willingness to kill, and even eat, those who didn't satisfy her. The implication in the tales is definitely sexual satisfaction, but it's important to note that rude or inhospitable behavior could just as easily offend. The Huldercarls' myths don't include the sexual implications of satisfy-or-I-kill-you, which perhaps reflects ancient Norse views on sex to a certain extent: it's possible to infer a supposition that females are harder to please, and therefore only those skilled enough could win her favor. At the same time, it's possible the Huldercarls' satisfaction was assumed simply out of an idea that males are less difficult to please, and also possibly that women weren't expected to "work" as hard at sex. MANY fairy myths involving sex imply that it takes great skill to satisfy a woman: this could also just be another area of prowess for the Hero cycle of a story.
In the earlier myths it appears the reward was protection by a superhuman entity. Imagine what Scandinavia was like before roads and effective land-clearing techniques: the forests were so thick and inhospitable they literally made isolated "islands" of arable land and could cut off huge swaths of area between towns. The Vikings weren't seafaring folk just out of convenience, but out of shipping and communication necessity. Dark things lived in those forests, from trolls to bandits to bears, and a Hulder whose favor you've gained could potentially protect you and your family from ALL of them. That's nothing to scoff at, and was actually so highly regarded even as Christiantiy took over the area the luck of befriending a Hulder was incorporated as acceptable practice.
Christianity spread over the Norse slower than the rest of Europe (indeed, partly due to the isolation of the land), but eventually it did effect the details of the Hulder/Huldercarl. One Christianized tale says the Hulder were once mortal children who weren't washed by their mother: the "unclean" children became Hulder. This isn't terribly different from the Christian myth of the Fae, who were God's angels who didn't take sides in the war in Heaven, and so fell but only to Earth, not to Hell with Lucifer and his band.
As time went on, the Huldra became pretty milkmaids who looked completely human and innocent except for the tail, but if a farmer could win her heart and convert her to the faith the tail would fall away (as she loses her fairy immortality and becomes mortal and "saved"). Hulder and Huldercarl lost their danger AND their protective abilities, and were relegated to rather benign figures in pastoral life: simple cattle herders who brought luck and prosperity if you were able to convert and marry one, but the threat had been nullified. Domesticated.
Of course, who knows if they were ever truly domesticated...
Norway, by the way, produces some wonderful movies about Norse mythology, including one about the Huldra. I saw it recently on Netflix, and recommend it if you're interested: Thale.