Charlie

Charlie, otherwise known as the Night Monster, or (unofficially) the Grue, is a hostile mob that never reveals herself. She only attacks in complete darkness when absolutely nothing is visible. Prior to her attack, the characters will give some sort of warning, such as "What was that?", and there will be a loud "whoosh" to signal her approach. 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.

The attack can be survived at least once, even without armour, most of the time. Usually, two hits will kill the player.

Not much is known about Charlie, but what is known is that she used to be human and was a friend of Maxwell before the Don't Starve world. This was hinted at through in-game tests and then revealed by Kevin on the 'Caves' livestream.

Light Sources
The following light sources will prevent Charlie from attacking:
 * Inventory/equipped items:
 * A Heat Stone at full charge
 * A Lantern while equipped or dropped (if not turned off)
 * A Light Bulb (on the ground)
 * A Miner Hat (while equipped)
 * A Pumpkin Lantern (on the ground)
 * Star Caller's Staff's Star
 * A Torch (while equipped)
 * Willow's Lighter (when equipped)
 * A Magiluminescense while equipped or dropped.
 * Structures or world objects:
 * A cooking Crock Pot (character must stand in front of it)
 * Fire (Campfire, Fire Pit, Willow-made fires, or burning objects)
 * A Light Flower (when not picked)
 * A charged Lightning Rod
 * A Mushtree
 * A Night Light (with fuel)
 * A Pig Torch (with fuel)
 * A Walrus Camp's light when a member of the MacTusk N' Son Hunting Party is occupying it (during winter)
 * Characters and mobs:
 * 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)
 * A Ghost's glow
 * Slurper (while it's awake and/or on the character's head)
 * WX-78 shortly after it's been struck by lightning
 * WX-78's sparks (when it's raining)

Trivia

 * The nickname Grue is a reference to the iconic monster from the game Zork. In Zork, the Grue only attacked players in pitch darkness after a line of warning, just like in Don't Starve.
 * Since Underground, Maxwell refers to the Night Monster as Charlie.Screen_Shot_2013-09-06_at_11.07.50_PM.png
 * The fact that Woodie is not attacked when he is in his Werebeaver form suggests that Charlie is not averse to light itself, but rather the act of being seen.
 * Charlie is Maxwell's assistant and it is speculated that she was transformed in an accident during a ritual.

Bugs

 * If a player enters a Worm Hole just before the night sets, Charlie will not attack when the character comes out of the other side. (This bug is stopped when going into light and then back into darkness again.)
 * If the player pauses the game when the sound of Charlie attacking begins and resumes right before the sound ends, Charlie will attack early.