"I have so many mouths, and I must scream."
It was believed that a witch could create this two-headed turd-snake by stealing a rib bone from a graveyard early on Whit Sunday, wrapping it in wool and storing it between her breasts. Next, she'd spit holy wine onto it at the next three Communions, after which it would come to life and start to grow. When it could no longer fit between Mama's jugs, she'd cut a nipple into her thigh for it to suckle.
Once it got big enough, the creature would roll its way to a neighbor's field and "lie across a sheep's back and suck two tits at the same time." When it was close to bursting, it would roll back home and vomit the milk into a bucket. The witch presumably did all this for the extremely vitamin-rich cursed-worm vomit-milk that Icelandic nutritionists are always touting.
"To stay young, suck on the secretions of the Falkor larva!"
Then there's the invisibility spell, which involved collecting "three drops of blood from the index finger of your left hand, three from the ring finger of your right hand, two from your right nipple, and one from your left nipple. Mix the blood with six drops of blood from the heart of a living raven, and melt it all with the raven's brain and pieces of a human stomach."