On the longest night of the year, the 15th day of the twelfth and last month of the year most human cultures celebrate the Ascension of Sabes, goddess of the night, the stars and magic. Colloquial calling it Sabes-Kimmin (roughly "The Arrival of Sabes" in ancient Baradolien language), but also referenced as Laudat Sabes in more conservative regions and sometimes simply Sabes-night
During this night from dusk till dawn all work stands still and the streets and houses and every area is filled with myriads of small, magical lights. Mages of all towns best themselves in spectacular magical light shows, illuminating the skies. These shows are usually called the "Dance of Light and Stars" and have their origin in the graduation ceremony of most magical academies.
The Ceremony of Enlightenment
At the evening right before dusk, traditionally all mages finishing their education during that year recieve their certificates in the Ceremony of Enlightenment. The most promising and successfull student ("Sabe Benedictus" or "Sabe Benedicta") will receieve their certificate last at the very moment of dusk and has the honor of starting the celebrations by letting their first light dance with a star (or constellation) of their choosing. Every student after them then choses their own star or constellation, which will in turn be referenced in their title from this night on. It is considered bad form to chose the same star as a student before them and many stars are associated with certain traits and destinies or famous wizards from the past.
The legend of Sabes-Kimmin
A long time ago, almost seven thousand years, when the gods still wandered among the humans, guiding and teaching them, when magic was still very common among mortals, there was a talented but ultimately unimportant mage, living as a humble servant in a town not worth mentioning in the outer parts of the glorious and illuminated kingdom of the gods, Ethoras.
Her life may have been unimportant, but it was good for Sabes and she was content. Until one night a god fell, and he fell right to the feet of Sabes, while she was watching the stars, that she loved.
And it is told that Sabes looked into the face of the fallen god and recognized him as evil and malicious. And indeed it was Zecod, who was cast down by his brother Apac for his misdeeds, but he was not yet defeated. Without hesitation, Sabes used all her magic and talent to hold Zecod down before he could flee, or worse, turn his anger towards that small, unimportant town that she called home.
It is said that the stars grew brighter and the air started to sparkle as Sabes drew on all the power around her, fighting the night she knew was the source of power for Zecod. The Darkness turned to light and danced around the stars, and the night turned into a spectacle of colors and magic. All while Sabes struggled to keep Zecod down.
But Zecod struggled as well, weakend by the fight with his brother and surprised by the force that hold him down. With every moment the night grew deeper though, nearing the point farthest from dusk as well as dawn, his power grew and he fought back harder and harder. Just in the very moment, Sabes' power would have been overwhelmed, Apac appeared and struck Zecod down, locking his powers away.
And Apac turned to Sabes and saw her, exhausted by the feat she just managed. This unimportant, unsignificant person - and he saw her talent and her resolve and he fell in love. He promised to return to her, just before he had to leave with his brother, to lock him away.
And Sabes waited a year, during which her life suddenly felt so small. And she wanted to welcome the mighty Apac back to that unimportant village she usd to love call home, but she felt sad and believed he would not return. And when a year passed by and the nights grew longer and darker again, she feared Zecod might have escaped Apac and would come back to spread the darkness everywhere. So on that darkest night, she began to light up the sky, began her first dance with the stars. And the mages all around her watched in awe, as this dark night suddenly turned bright and beautiful and they joined in in the dance.
It was during this spectacle, that Apac returned and he saw Sabes in the centre of light and magic and his love for her grew even deeper and from this moment on she was the most important person for him forever. He took her with her and travelled with her to the stars she loved so much and showed her the way to the heavens. And on this night, Sabes ascended to the sphere of gods, taking her place besides Apac, and together they ruled equally and peacefully over the gods and mortals and all the world.
Non-human Races
All four races recognize Sabes as part of the golden pantheon but they do not celebrate Sabes-Kimmin as most human cultures do. Still most of their rituals at that day contains elements of lighting up the darkness.
Elves
Similar to humans, Elves use this night to celebrate the stars and magic. They do not use this as a graduation ceremony but rather as part of the final test. It is in this night, that the darkness takes on forms on its own, especially in magic filled places the Elves live in. Those creatures, called imps are annoying and mischieveous but usually not dangerous. Young magicians have to test their might against the imps, banishing them into the stars, where they will be bound for another year.
The elves believe this was the actual origin of the human festival as well and they are of the opinion their dance with the stars is helping fortifying the prisons of the imps.
Orcs
The Orcs are also aware of the threats that roam the darkest night and they protect each other by lightijg up the night with a huge bonfire. This fire is also a time for coming together and celebrations and it is this night, where the older shamans teach younglings of their tribes of their culture and the rituals of the year to come.
Dwarves
Yes, even the dwarves light up this night in their great halls under the mountain. In fact they make a point out of lighting up every room, corridor and corner in the most creative and colorful ways. They completely avoid the use of magic in this night, as they believe it would lure the creatures of evil into their halls. All the better that the others are literally displaying fireworks of magic. Also their earlier experience of mixing Magic and celebrations with lots and lots of alchohol was a painful one and an important lesson learned for the dwarves.
I really like the sense of history to the holiday and the tie into religion. I also enjoy that you show a bit on how the different races observe it.