The witches didn't used to be evil, explains Johan Egerkrans, author of Fairy Creatures of the North (Nordiska Väsen), an anthology of Nordic mythical creatures that explains everything from hobgoblins to milk-hares.
"Magic permeated the old peasant society, it was something everyone dabbled in, even though the church didn't much like it," Egerkrans says.
Many old traditions live on - throwing salt over your shoulder to prevent bad luck, staying clear of black cats - but it's become routine, rather than ritual.
"All our superstitions come from old beliefs, and originally witches were seen as wise old men and women, who knew what herbs to pick for healing," he says.
Being good at gardening would soon turn sour, however, as the witch hunt reached Sweden.
"The only permissible magic tricks where the ones performed in church," Egerkrans says. "Everything else had to do with the devil."
So anyone who tinkered with magic was all of a sudden a bad person.
Walpurgis Night, meant to welcome spring, became the night that the witches travel to Blue Mountain, or Blåkulla, to fraternize with the devil. Fraternize is a rather weak word for what they actually did up there. Once the witch hunt reached Sweden, suspects told the tribunals in rather fine detail what they would get up to with the devil.
"Mass orgies," says Egerkrans, before bursting into laughter recounting some of the rather disturbing descriptions of what sex with the devil felt like (scales and clamminess are involved).
But how did the witches get there? On a regular old broom? Yup, but back to front.
"And what you might notice straight off is that they travel there naked," Egerkrans says. "It's not Harry Potter-style broom riding, as it's back to front, and you could also travel in a milk pail."
"The ritual on the mountain was also back to front and upside-down, because everything had to be the opposite (to how the church did things)," he explains.
"There was a very dualistic world view back then, which actually stayed with us in some ways until the 1960s. Before then left-handed Swedish children weren't allowed to write with their left hand in school, because the left side was associated with evil."