Grim

When Harry finds himself being followed by an enormous black dog, he suspects that the creature might be a grim, a spirit in the form of a menacing dog that has long been known in the British Isles as the "omen of death." Luckily, the beast turns out to be Harry's godfather, Sirius Black, who can conviently transform himself into a dog at will.

By most accounts, grims never leave the churchyards or burial ground that they inhabit. In both British and Scandinavian folklore "grim" can be a general term for a household spirit, but it is more commonly used to refer to the "church grim," a guardian of dead souls that in England takes the form of a big, shaggy, black dog with fiery eyes. In Scandinavia, the church grim may also appear as a horse, pig, or lamb.

According to English tradition, the church grim bears the heavy responsibility of protecting the graveyard from witches. In the early Christian era, many people believed that when a new churchyard was created the first person to be buried there would have to guard it. But some also believed that if a pure black dog was buried in the northern part of the churchyard, the animal could stand guard instead, freeing a human soul to go on to the afterlife.

Grims are usually invisible, but during stormy weather they can be seem roaming about the churchyard. They may also appear at midnight on the night before a death, or standing in a church tower during a burial. It is said that the clergyman delivering a funeral service can tell from the grim's appearance whether the soul of the deceased is destined for heaven or hell.

Werewolf

In folklore from around the world, a werewolf is a human with the capacity to transform into an unusually fercious wolf. Active only at and often (but not always!) under a full moon, he devours men, women, children, and livestock, ripping out their throats with his claws and fangs. In some stories, a man who becomes a werewolf is the unwilling victim of a curse or a bite from another werewolf. Much as the victim hates the harm he causes, he is unable to control his actions. In other tales, a sorcerer makes a conscious decision to become a werewolf - often by using an enchanted belt or special ointment - so that he can carry out his terrible deeds. Although werewolves are almost always men, tales of female and child werewolves also exist.

Tales of man-wolves have been around for a long time. Greek mythology tells of a bloodthirsty tyrant named Lycaon who greatly angered Zeus by serving him the flesh of a human child. As punishment, Zeus turned Lycaon into a wolf, although he retained some of his human features. This story is the source of the word "lycanthrope," another term for werewolf.

Werewolf legends and beliefs were fully underway in Europe by the early Middle Ages. Surprisingly, the image of the werewolf during this time was not all bad. While in some stories wicked stepmothers and villians turned out to be werewolves, in others the werewolf might be a hero, a saint, or a comic figure!

By the 16th century, however, werewolves were no longer portrayed as heroes or figures of fun. Instead, they were regarded as a very real threat. As witch persecution gained momentum across Europe, dozens of people in France, Switzerland, Germany, and Italy were arrested, tried, and executed for being werewolves. Accused of horrific acts of mass murder and cannibalism, many of these alleged werewolves confessed under torture.