White Hair is a condition that occurs in females of the Alluthian People, almost always of the humans of Yun Alluth. It is extremely rare, occuring in only 1 in a million girls. The Alluthians believe that a girl born with white hair is a reincarnated personification of Vreathe's Moon Goddess Kalbeth. If a girl is lucky enough to be born with this condition, they are designated the Avatar of Kalbeth, and can expect to live a care free life of luxury. If a girl is born with this condition and there is already a living Avatar of Kalbeth, they can expect to die, very quickly and brutally, so the people of Yun Alluth are left unaware of the nature of the white hair and continue worshipping the moon goddess.
In reality, most Alluthians are in fact descended from the moon goddess, who was said to have glowing white hair. Every so often the genetic mixture is just right and a girl is born with this condition. This doesn't offer any special abilities or take away any ability that any human would have. It's just a genetic marker of the moon goddess. With training, a mage can make their hair store excess mana, but white hair offers no advantage over other types of hair either.
There are stories of girls being smuggled out of Alluth that are born with white hair, enough that they are known to exist as far away as Cassel, Faeon, and Teross, over a thousand kilometers away. The vast, vast majority of these white haired Alluthians lives in servitude or are kept as human pets by rich elves of the lands of Teross.
It should be noted that every dozen generations, the genetic code is mixed such that an actual Avatar of Kalbeth does manifest in a white haired girl. Her magical ability is thousands of times greater than any human and she gains knowledge far beyond that of even the most experienced sages. It has been over a thousand years since an actual Avatar of Kalbeth has manifested herself though. Even worse, as of the year 1980, the current Avatar is dead and no replacement has been found. There is no white haired girl living in Yun Alluth at this time. This has caused the nation to send mercenaries across the continent in search of a suitable candidate to become the next Avatar of Kalbeth. Without her presence, it is said that the country will fall apart and the people will die.