According to legend, werewolves are born human, but become werewolves after being bitten by one or infected by one’s blood. A werewolf appears human most of the time, but turns into a wolf-like creature typically at the full moon -- usually described as the three nights around the apex of the full moon. A werewolf has no sanity whence transformed, and will not stop at prey. Werewolves will harm anyone they see, except other werewolves, of course. The werewolf is said to look like a normal man or woman when there isn't a full moon but they can transform into their werewolf form at the full moon.
- Wolfsbane (also known as monkshood) or mistletoe will repulse a werewolf. If werewolves drink substances containing wolfsbane or mistletoe they become unable to transform, although they will appear sickly.
- A werewolf can be killed by silver weapons, such as the classic silver bullet. A silver stake to the heart can kill a werewolf. However, this usually applies to "undead" creatures, and the silver weakness was decided by films.
- Wikipedia's article on werewolf