Willow

Willow is the first unlockable character (160 XP, see Experience for more information on how to unlock her). She is immune to Fire damage. When she is submerged in complete darkness, she starts a fire at her feet before Grue comes. However, this fire can spread and burn resources unintentionally, for example forest fires. This may cause trouble when collecting resources but it may be a safe, resource-free way to survive nights. Only down side to this is that she has to be submerged in total darkness for a while, which will start making her insane.

Willow is a slut but I would fuck her brains out.

Strategy
Willow is generally considered a "beginner" character due to the nature of her special trait. This is most likely why she is the first unlockable character.

She is meant to help new players that may have trouble adapting to the Light mechanics of Don't Starve. Players that are unaware of the necessity to gather Logs and Cut Grass during the first Day-Night Cycle in order to survive the Grue will be happily granted access to Willow after surviving a cumulative total of only 8 days as Wilson.

Typically, when more experienced players plan for a day of scavenging away from their camp, they will always bring ample Logs and Cut Grass, or ensure they bring an Axe so a Campfire can be made to survive the night without relying on Willow's special trait, which comes inherently with a large loss in Sanity due to the necessity of being immersed in total darkness to activate it.

Furthermore, Willow's immunity to Fire damage is negligible at best. The reason is twofold: One advantage to her Fire immunity is in the event of a lightning stike near the player while in an area with combustable objects; the player won't have to worry about any damage. Again, lightning is rather unpredictable and this advantage also falls under situational.
 * When a player is standing in Fire, there is a built in 1-2 second delay before damage is actually calculated. The screen will glow with flames on the bottom providing an extremely obvious visual cue to move in order to avoid damage. Even while standing in flames for extended periods, the damage is still negligible if even one piece of Armor is currently worn.
 * Fire simply isn't a common threat for the majority of the game. Unless the player is deeply immersed in heavy Forest while it is burning, avoiding fire damage is trivial. Spiders, Tentacles, Hounds, and Killer Bees all provide much greater threats to the player on the higher survival days than Fire does. It is basically almost never an obstacle to the player, and when it is, it is almost always subject to a very unique and uncommon circumstance, making Willow's Fire immunity bonus very situational at best.



Willow will be of the most use when the player, for some unexpected reason, is caught in Night with no source of light, and no way of making any. This can obviously happen for several reasons, like when Night Hands begin stealing the flames of the player's campfire, if Frogs happen to remove the items necessary to make a fire from the player's inventory, or if the player just plain forgets to plan for it. During these unforeseen circumstances, Willow's fire ability will definitely be an undeniable advantage. However, these situations are again very circumstantial and usually only apply to newer players that haven't quite experienced every threat that awaits the player in the wilderness, helping further justify the fact that Willow is a character tailored for aiding against the threats that tend to plague beginners more than advanced players.

Advanced Strategy
Although Willow is regarded as a beginner character, there are some unique advanced strategies she can pull off. Most notably, Willow can provide probably the most efficient start as of The End of the Beginning update, second only to Wickerbottom. This is due to her immunity from the Grue. She is capable of scavenging useful resources all night, foraging for Blue Mushrooms, working through the night chopping trees, and even has a natural advantage for shaving Beefalo with a Razor at night. Couple all of this with the fact that you will have higher exploration potential and resource gathering, which are arguably the most important things to do during the first 10 days, and Willow can make for a very strong start given fact that very little productivity is lost at Night with her.

All of this comes with a downside: running through the night recklessly and relying on her flame to activate will often result in running headfirst into dangerous scenarios or igniting natural resources such as Grass, Saplings, and Trees that would have otherwise been gathered. Again, this is why working through the night is high risk, but can also come with high reward, and is only recommended for more advanced players.

Trivia

 * Willow's voice is sounded by a flute.
 * She appears to have a mental illness called pyromania. That means she cannot resist mental urges to start fires.
 * Willow is based on "The Firestarter" novel from Stephen King.