Fairies are mysterious but dangerously cunning magical creatures that used to live outside the fillorian kingdom. They once dwelt within a mysterious plane that occupied the same space as Castle Whitespire known as the Fairy Realm.
They are known for their insidious terms, as well as their unconventional way of expressing themselves, resorting to riddles and puns. The fairies now live as citizens of Fillory after King Margo provided a large settlement for them to live in peace.
Fairies were originally creatures of Earth. Around the 1600s, they were being hunted nearly to extinction when humans discovered that inhaling fairy dust, fairies grounded to powder, would grant temporary fairy magic. Having found a new world, the Fairy Queen made a deal with the McAllisters, a prominent family of magicians, to save her people. The family would not be able to follow them if some were left behind and became their servants. The volunteers were then bound for life with a fairy collar that would prevent them from using magic by automatically killing the should they perform any magical acts. Because of this deal, the fairies were able to escape to Fillory and create a new home with a golden key..
The Free fairies
In time, the Fairy Queen died along with the knowledge of the deal and the queendom was passed to her daughter. Because of their history, fairies have a deep distrust of humans and would only be summoned out of their realm to make complex deals with steep prices. Eventually, they develop a reputation as mercurial and powerful beings that are feared by many..
Because their realm did not provide the proper conditions to plant fairy eggs, they could not reproduce and only had human children that were bargained away.
The Earth Tribe
After 400 years, the McAllisters bred more fairies for captivity. The newer generations never knew they had magic and were made to believe that they were being protected by the McAllisters as the last tribe of fairies. A fairy named Dust was the last survivor of the volunteers. Unsure if his Queen had survived the journey to the other world, he lost all hopes as he saw his kind suffer and die one by one.
The fairy presence in the McAllister family was kept a secret although it made them one of the the few magicians with a source of magic after magic was cut of from all the worlds. Co-currently, they were also being grounded into fairy dust for the family to continue to use magic.
The fairies were eventually freed when their new Queen broke their deal with the help of Fen and Julia Wicker allowing them to massacre the McAllisters save for Irene and reunite with their people at fillory. 
Fairies usually cannot be perceived by humans. To do so, they must make a deal with a fairy, have a deal made on their behalf or use the Truth Key.
Each fairy have the appearance of pale humanoids that possess large black eyes, pointed ears, slick back hair and a lack of eyebrows. They thrive in moist and humid environments which they also require to plant fairy eggs. In the absence of such conditions, fairies would compensate by taking long baths.
Like other Magical Creatures, fairies have magic independent of the Wellspring and can perform great acts as the the '"living embodiment of magic". Fairy magic is powerful and ill-defined which they use to make "deals" to leverage for power, levitate and perform other acts such as fixing the Wellspring. It does not require hand gestures or words, simply their mind, as shown when Sky created a flower in her hand simply by imagining it.
The body of a Fairy can be reduced to a cocaine-like powder that, when snorted, allows magicians to perform fairy magic for a certain amount of time. However, fairy dust does not appear to be compatible with humans and can suffer physical ramifications in the form of physical illness and tissue decay with prolonged use.
Fairies are known to make complex deals with steep prices. Deals are said to be the foundation of their culture and use as a means of survival. Thus, asking help from the fairies can be risky and would be advised against it, even as a last resort.
When a fairies are first petitioned, they uses a human ambassador to negotiate terms. If insulted or vaguely dismissed, the ambassador will only honor the present deal without further amendment.
According to Fen, they associate with powerful people in secrecy and are known "tricksters". Once a deal has been made, it is impossible to change one’s mind or to bargain for another solution. When the terms are set, the fairy will deliver what is requested from them and get what they ask in exchange. The person who made the deal will then be able to see fairies. If the person who made the deal have someone else pay the price, the person affected by the deal will also be able to see the fairies. The only other way to see a fairy without making a deal with them is by holding the Truth key.
Fairy deals can only be broken by the Fairy Queen using her blood to paint a specific rune, though she stated that breaking fairy deals have consequences. Once a deal is broken the humans who could perceive fairies as a result of the deal will instantly loose the ability to perceive them.
- The Earth fairies were exploited by the McAllistair who grind them down to a powder which gives humans temporary fairy magic and sold to the Order as part of a deal.
- Fairy magic has a noticeably darker appearance to other magic, possessing a more smoky quality.
- The Truth Key can reveal fairies to the holder regardless of whether or not they've previously made a deal with a fairy.
- The Fairy Queen promised there would be consequences for her breaking the deal. What they are remains unknown.