Werewolf

The Werewolf is a Hardmode enemy that only spawns at night while a full moon is active, during which it is as common as Zombie. Werewolves can open doors and have a chance to inflict the Bleeding debuff. At close range, Werewolves attack the player by leaping or lunging, closing distances quickly to catch unwary players off-guard.

The Werewolf can drop the Moon Charm, which allows the player to transform into a Werewolf at night.

Tips

 * The nights on which Werewolves will spawn can be tracked through the items that certain NPCs sell, as the Painter sells paintings based on the moon phase, and the Clothier will sell unique items specifically during a full moon. The inventories of the Dye Trader and Skeleton Merchant will also have unique items, though a or derived informational item provides this same information much more directly.
 * Using a Water Candle and/or Battle Potion can be useful for farming the Moon Shell and later the Celestial Shell.
 * If under-powered on the night of a full moon Werewolves can be fought regardless using the same strategies one might use against early-game Zombies, such as boxing oneself into safety and opening a small hole to release projectiles from.

Trivia

 * In common lore, the main weakness of werewolves is silver (e.g., Silver Bullets), but silver items in Terraria offer no particular benefit in dealing with them.
 * Werewolves in Terraria share the trait of roaming during a full moon with common-lore werewolves, however.