The Livonian Christmas werewolves
Men changed into wolves gather on Christmas night, attack people and animals, and lay siege to houses standing alone in the woods.
The account Sabine Baring-Gould quotes in The Book of Were-Wolves names no one. On Christmas night, it says, great numbers of men changed into wolves meet at one place and then go out to attack people and tame animals. The people of the region, it says, lose more to these than to real wolves. When the wolves find a house standing alone in the woods, they lay siege to it and try to force the doors, and if they get in they eat everyone inside.
Wikipedia's article on the werewolf cites the 16th-century Swedish writer Olaus Magnus on the Livonian werewolves. By his account a man became one by drinking off a cup of beer brewed for the purpose and reciting a fixed formula.
A 2016 post on the Oxford University Press blog credits the Christmas account to Olaus Magnus, and gives the werewolves' range as Prussia and Lithuania along with Livonia. It adds that at one castle the werewolves held games, and the others ate any that were too fat to clear a wall.
"“On the feast of the Nativity of Christ, at night, such a multitude of wolves transformed from men gather together in a certain spot, arranged among themselves, and then spread to rage with wondrous ferocity against human beings, and those animals which are not wild, that the natives of these regions suffer more detriment from these, than they do from true and natural wolves; for when a human habitation has been detected by them isolated in the woods, they besiege it with atrocity, striving to break in the doors, and in the event of their doing so, they devour all the human beings, and every"
- Werewolf, Wikipedia contributors, en.wikipedia.org
- Witches, werewolves, and Christmas, OUPblog, Oxford University Press