Interesting, thanks!

True that, the are commonly portrayed as vampire rules but they are more of less for lesser supernatural beings. Also vampires is more of a family name than a certain specific creature as it is portrayed in popular culture today. Vampires are simply beings that feeds on humans. In Swedish the translation of nightmare is a mare-dream (mardröm) and a direct translation of nightmare - Nattmara - is a creature that creates nightmare to feed of your fear. They are spiritual creatures that have no material form and they are a form of vampires since they feed on humans. They aren’t exactly dangerous nor are they inherently evil, no more than wolves or lions or other predators. It’s just that what they feeds on is quite bothersome for us human. They won’t actually hurt you, just scare you, the sleep deprivation might eventually though. Old beliefs say that holy water and prayers and crosses and stuff works. Even older sayings does not. It’s less about what actually works and more about what you believe works and what makes you feel safe. They aren’t found of silver, salt or water though. Following some of the old rules for supernatural entries. Iron might work but is more for fae/fairies. For all of these rules about substances there is one important rule though. It has to be pure. Pure silver. Pure iron. Pure salt. But you can mix pure salt with pure iron for some reason.

If you have a night mare haunting and hunting you it will eventually show itself to you in the waking. They are all female according to mythology and it’ll usually take on a terrifying form. A dead old woman or a demon woman or such and it’ll launch itself at you as if attacking but then dissipating and disappearing. If you have issues with one salt around the bed, a bowl of water under the bed, throwing water or salt on it or burning sage are the old school DIY recommendations. Best recommendation is to call for a völva, which is an old Norse title for a person/woman that’s a witch/Shaman/priestess/healer/seer. It was their job to handle things like that. Or try to carve some protective runes to put under your bed/mattress.