The following is summarised from the writings of many Llaeffi'r scholars on the origins of this world.
It is no easy thing to speak with certainty on the creation of Ashagon. That it was created is, of course, indisputable; from the fertility of soil to the vigour of wind evidences abound of this world being a living thing, and all that lives must once have been born and will one day die. Models of an eternal Ashagon, without beginning nor end, describe a static and dead world so absurdly alien to reality that any philosophies arising from it may be dismissed in their entirety as foreign heresy.
Yes, that this world was created is indisputable, agreed by most peoples of Ashagon. There is sadly much less consensus on who created it. Again evidences of their nature can be found in common observation of the natural world, but they are sadly open to misinterpretation (wilful or otherwise) as seen in the many differing faiths of Ashagon's peoples misattributing the Great Creation that is this world to lesser and even false deities.
Fortunately, Faeries do not have to rely on mere observation and intuition alone. Llaeff- She Of Many Faces, She Who Cares for the Small and Underdog, the divine patron of all Faeries- is the only party involved in Ashagon's creation still residing within it, and so an objective source on its nature. She walks amongst the many people of Ashagon wearing many faces and personas, and it is from her teachings as Saint Aethrawes that Faeries credit most of their knowledge on Llaeff's divine brethren, the Crwydoedd.
The Crwydoedd collectively created Ashagon. This is a truth affirmed by basic intuition; the greatest mortals creations require the work of many artisans, so it should not be any surprise that the greatest of creations, Ashagon itself, is the fruit of many divine hands. From Saint Aethrawes scripture we know that though the Crwydoedd of divine power, they are possessed by the same motivations as us mortal peoples. They created this world, and indeed many other worlds, for the multitude of reasons any who create do.
Ashagon is the product of both competition and collaboration. Its great mountains are the outcome of playful boasts on who could raise the tallest peak; its sun a united effort to make something shine like no other. This world's peoples range from the products of careful design and frivolous fancy, but all of us were made with intention and in some small way deemed to improve Creation. Saint Aethrawes emphasised above all else that the Crwydoedd's creation of Ashagon was a joyous one.
Eventually (the time impossible to measure, as Ashagon's time was something created during this era), the Crwydoedd deemed they had created all they could within Ashagon. The Crwydoedd are innately travellers- Ashagon was neither their first world nor would it be their last. To add more to this world would only be to muddy what had already been made, and so they departed for a fresh canvas.
All departed, except Llaeff. She who was the youngest and most curious of her siblings, who had crafted the moon and lakes and countless more, chose to remain here in Ashagon. Saint Aethrawes did not speak on if it was common for Crwydoedd to linger in the worlds they created, but given how strongly she described the Crwydoedd's nature to roam Llaeffi'r doctrine has inferred Llaeff's choice to be a deep act of love. Ashagon is likely unique among all the Crwydoedd's worlds for it.
Many Faerie saints have spoken at length on why they stayed on Ashagon even as their brethren left. Llaeff had grown attached to this world and its peoples. She wished to experience the world the Crwydoedd had created as their creations did, to cloak herself in our forms and walk Ashagon as we do. Unlike the rest of her brethren she did not believe that the potential for new stories had ended just because the era of creation had. She would work to ensure it had not; guiding us in our times of uncertainty and challenging us when we became set in our ways.
If life is one thing it is dynamic. It exists in motion, in change, in its potential to be different and greater tomorrow then it is today. Llaeff remained to witness and encourage that growth.