A werewolf is a person who turns into a deadly wolf-like creature once a month on the full moon. Although they may seem ill as the full moon approaches, they are able to live as normal people for the rest of the month.

Werewolves cannot transform by choice and the transformation is incredibly painful. When in wolf form, they no longer remember who he/she is, and are crazy and reckless, like someone with rabies. They lose the ability to think in a human way, becoming highly aggressive towards humans—even friends and family. They will bite and sometimes even kill anyone if there's an opportunity to do so. Though werewolves usually only infect their victims by biting them, they sometimes take it too far and kill their victims. However, they tend not to to attack animals, or even Animagi (in animal form). Without any humans nearby to attack, or other animals to be with, the werewolf will attack itself out of frustration. This leaves many werewolves with self-inflicted scars and premature aging from the difficult transformations.

Werewolfism is a magical condition known to be spread by saliva-blood contact. A human bitten by a werewolf in wolf-form will become a werewolf themselves. Also, it can be inherited—if one or both parents are a werewolf, the child may also be one, but this is not always the case.

There is no known cure for being bitten by a werewolf. The Wolfsbane potion is the only known potion that can help werewolfism. The potions allows the werewolf to keep his/her human mind during transformations. Also, being around other animals helps werewolves (in wolf form) keep their mind more than they normal would.

Werewolves can be easily distinguished from regular wolves by several small distinguishing characteristics, such as the pupils of the eyes, the snout shape, and the tufted tail.