Mab y Draig

The elves built their village on the mountain where the dragon dwells, gaining peace by living under its protection.
To prevent the dragon from waking and leaving, they preserve a law that continues to offer the “white child” the dragon demands.

A child said to be born without pigment at a rate of one in twenty thousand. They share the same appearance: white skin, white hair, and red eyes, and village law marks that form as something exceptional.
In a distant past, or perhaps a distant future, or even beyond this world, the dragon was deeply bound to a white girl. Seeking the faint echo of that memory, the dragon desires the white child.
When a white child is offered to the dragon, the dragon returns to sleep and peace is preserved across the land. So the village has long believed.

The serpent was an indigenous god handed down in the homeland of the brown elves.
It is not a great god like the dragon, ruling a mountain, guarding its people, and demanding offerings. The serpent crawls across the earth, passes through burrows, slips between corpses and roots, and returns what has been lost to the soil.
War destroyed that faith together with its village, and almost all scriptures and ritual implements were lost. Now, its full shape remains only in the memory of Eris, its priestess.
The serpent changes into the “World Eater” not because this god was an evil deity destined from the beginning to destroy the world. The serpent opens its mouth according to the amount of loss and hatred offered to it. If its power swelled to mythic scale, that proves not that the serpent was strong, but that the world took too much, beyond the order of nature.