Day of Luminance

Every four years, the Bright peoples of the world hold a festival at the top of Mount Cadrehal, the tallest mountain in Orliüm. It takes place on the Day of Luminance, the longest day that occurs within that time. On this day, wizards long past opened the sky to allow the full power of the sun to reach the world. The cataclysm that followed with the arrival of the sunbeasts ravaged the peoples of Orliüm, but those who survived and continue to live on the surface consider themselves to have great strength. It as at this event that the most powerful Brightcasters gather from across the surface, risking travel from their protected towers to bring themselves as close to the source of their power as possible. There, they perform a dangerous ritual that will bring their apprentices and other potential bright mages into their full power...or not.
Those tasked with preparing for the festival place two rings of sunstones in the hours before dawn. The outer ring encompasses the entire mountaintop, while the inner ring is perhaps only one hundred yards across. Within the halo of sunstones, the attendees are protected from the threat of sunbeasts and the direct magic of the sun. The actual festivities begin at daybreak with a feast.
The highlight of the day is the Illumination Trials. At high sun, all the apprentices and hopeful Brightcasters must step over the inner ring into the unprotected space. There, the initiates must stare into the sun in an attempt to channel its full power into themselves, thus proving that they can control luminance magic. If an initiate can harness their power unharmed, they are granted full status as a Brightcaster. Those who are unable to suffer terrible consequences. 
Some are struck blind, and lose the vast majority of their power. These "Blinded" are considered to be weak and unworthy to wield the sun's magic. Blinded potentials are almost always shunned by their community, and even their own families. Many are abandoned on the mountaintop at the conclusion of the ceremony, left to their fates. The Blinded are fortunate. Many of the potentials are either driven insane from gazing into the pure magic of the sun, or lose control of their power and burn alive. Often, only two dozen potentials are expected to survive the Trials.
A luncheon is held after the Trials are over, though the mood is usually far more subdued among families who have lost loved ones in their attempt. The Brightest of the wizards then make several speeches; they offer praise to the ancient wizards who granted them this power, and reticule the cowardly Darklings who live underground. The final meal of the day is taken before sunfall, wherein the Brightcasters will accept new candidates for apprentices to return with them at the conclusion of the festival.  Some Underdwellers have made attempts to sabotage the Trials to prevent the rise of more Brightcasters, though all have failed.