Charlie

Grue
The Grue (officially Charlie) never reveals itself. It only attacks at night, in complete darkness, when absolutely nothing is visible. Prior to its attack, the characters will give some sort of warning, such as "What was that?" or a loud noise. Moments later a slashing sound is heard and the character will take 100 damage and 20 Sanity loss, and 10-20 damage when moving. This will continue to happen until a light source is found, or until the character dies.

There is a small chance of surviving the attack if the player is equipped with Football Helmet, but it causes the helmet to lose 50% durability. Also regardless of staying in Cave, the player is still attacked by Charlie under complete darkness.

Light Sources
The following light sources will prevent Charlie from attacking:
 * Fire (campfire or burning objects)
 * A Torch (while equipped)
 * A Miner Hat (while equipped)
 * A Pumpkin Lantern (on the ground)
 * A charged Lightning Rod
 * A cooking Crock Pot
 * A Heat Stone at full charge
 * The Lantern while equipped or dropped (if not turned off)
 * A Mushtree
 * A Light Flower (when not picked)
 * A Light Bulb (on the ground)
 * Willow's flame
 * Willow's Lighter
 * A Walrus Camp's light when a member of the MacTusk N' Son Hunting Party is occupying it (during winter)
 * Willow will suffer from great Sanity loss while in total darkness.
 * Abigail's glow
 * Fireflies' illumination.
 * Coming close to them will cause them to disperse. If players walk away, they will come back almost immediately, making it possible to "hop" between two or more patches of fireflies and survive the night. It can even be done with just one patch, walking in and out of repeatedly, although this is more difficult and the player suffers greater sanity loss.
 * Coming close to them will cause them to disperse. If players walk away, they will come back almost immediately, making it possible to "hop" between two or more patches of fireflies and survive the night. It can even be done with just one patch, walking in and out of repeatedly, although this is more difficult and the player suffers greater sanity loss.

Trivia

 * Grue appears to be a reference to the iconic monster from the game Zork, the Grue. In Zork, the Grue only attacked players in pitch black darkness, just like here in Don't starve.
 * Since Suprise! Story Preview Test, Maxwell refers to the Grue as Charlie. Maxwell says, "Its getting Dark, Charlie will be waking up soon!"
 * Grue is the name of the sound of a blade slashing in a very high pitch.
 * As disclosed by one of the developers on the livestream of the pre-alpha Caves update, Charlie was once a friend of Maxwell and is actually a girl.
 * When Maxwell hears the sound of Charlie, he says "Charlie? It's me! Maxwell!"

Bugs

 * If a player enters a Worm Hole just before the night sets, Grue will not attack you when you come out of the other side. (This bug is stopped when going into light and then back into darkness again.)
 * If you pause the game when the sound of Grue attacking and unpause right before the sound ends, Grue will attack you early.