Long ago, somewhere in the multi-verse, a pair of twin Fay were born. Though, born is not the right word.
In the truest sense, the Fay are not alive. They are ageless spirits whose form shifts with time and location. Some do die, or are destroyed, and some new ones come into the world, but mostly they are eternal.
They can be found wherever life blossoms, from simple microbes to complex eco-systems. Some scholars say they are an manifestation of the souls of the trees in a forest or the fish in a stream. Other say that they are the cause of life. That these spirits turn chemical reactions into living creatures.
Mostly they remain hidden, dormant even, letting the millennium slip by, one season after another. But in some places and times they take more physical form as dryads or treants though these are usually solitary creatures.
With the twins, something different happened.
Unlike their solitary cousins, the twins discovered the benefits of working together. With a common purpose, they could combine their powers to protect and improve their homes. They nurtured and cultivated life, bringing new Fay into existence. For the first time, Fay were created by choice.
These new Fay were different, they copied the twin's physical form and worked for them, creating yet more Fay. In time, a civilization bloomed that mastered the fundamental forces of the nature and spread itself across the multi-verse.