To keep things basic.
The contract was divided into three parts.
First is that anyone can form a general contract with any of the fairies. It's the most basic form of contract and it's given as a form of blessing to those whom fairies consider their close ones. In this type of contract, a blessing is issued, which increases the natural elemental affinity of the one whom the blessing is given to.
Second level of contract is when the fairy is forming a close bond with any being. In this type, the fairy can allow the user to use most of the spells which she herself can use. This type of contract is more like a form of marriage where the fairy decides to spend her life with another being of another race.
Though this type of contract can be broken as well… at the price of losing one's energy and starting from scratch. Though the power of the user to whom the power was given remains, still the same.
