I’ve been looking a bit into witches, and I latched onto one physical trait the Russian Baba Yaga is sometimes said to have, which is iron teeth. Such teeth seem to be associated with witches in general in Slavic lore. One Russian tale I came across, “Prince Ivan, the Witch Baby, and the Little Sister of the Sun,” starts with a royal couple who are so ashamed of their mute son that they wish and pray for another child, only to be punished for their treatment of the first child by having a daughter who’s a witch with iron teeth. She eats the parents, but Prince Ivan manages to escape on a fast horse on the advice of the stable groom, and is somehow able to talk after this. He encounters two old women and two giants and asks to stay with them, but they refuse him because they’re being forced to perform a particular task for the rest of their lives, sewing for the women and throwing trees and mountains for the giants. Finally, he comes to the castle of the Little Sister of the Sun, who befriends him and gives him magical gifts that create more trees and mountains for the giants, thereby extending their lives, and apples that make the women young again. He confronts the witch-baby and once again escapes from her. The witch is said to use her iron teeth to gnaw through trees and mountains in her way during her pursuit of Ivan, but breaks them by gnashing too hard after he finds refuge in the Little Sister of the Sun’s castle. In another, a witch chasing a boy named Ivashko forces a smith to make her iron teeth in order to chew through a tree. This story also has Ivashko trick the witch’s daughter into cooking herself in a manner reminiscent of that in “Hansel and Gretel,” after which the witch eats her own progeny. And the German witch Perchta is sometimes said to have an iron nose.
Maybe some of them also have iron breasts, which would explain why a witch’s tit is regarded as being so cold.
Slavic mythology also has the psoglav, information on which is rather scant, but it’s said to have a human torso, the legs of a horse, and a dog’s head with a single eye and, yes, iron teeth.
They live in caves and eat people, including digging up graves to devour human corpses. And to get away from Eastern Europe for a bit, in the Akan mythology of southern Ghana, there’s the Asanbosam or Sasabonsam, a sort of vampire ogre with iron hooks for feet.
Some interpretations make them more bat-like, and will use “Sasabonsam” specifically to mean the chiropteran variety.
The association of witches and monsters with iron teeth and other body parts is interesting because, in other parts of the world, iron is said to ward off witches and demons.
In Britain, it was considered the bane of fairies, and that presumably expanded into being protection against other sorts of magical beings.
It appears to be a pretty common occult belief that magic won’t work on iron, or that the metal at least has a dampening effect on it. I’m sure the supernatural properties of iron come at least partially from its magnetism and conductivity, as well as how it makes more durable tools and weapons than bronze. Iron-working led to an increase in technology, so it can represent the power of humanity to tame nature. In the Finnish Kalevala, iron was poisoned by a hornet while the legendary blacksmith Ilmarinen was first tempering it, so it came to be primarily used for harmful implements.
This account also says that iron came into existence where three goddesses had squirted out their breast milk onto the ground.
This page suggests that iron symbolized the victory of Christianity over the more nature-driven pagan religions, and that in Britain it was used to fight off the native Britons, who only had bronze weapons. I know I’ve seen the Wicked Witch of the West noted as an exception to the rule of witches not being able to work magic on iron, as she specifically makes an iron bar invisible to trip up Dorothy. But then, in the late nineteenth and early twentieth century United States, iron would have been considered much more commonplace than it was to the writers of old folklore. The Tin Woodman might well be mostly made of iron, since tin doesn’t rust, but he doesn’t talk about that part of his metal composition. In the Russian Magic Land books, he’s actually called the Iron Woodman.