Gathered Eye Syndrome
The pilgrims traveled in groups toward the land of their faith—Mount Grail—ignoring the effects of the Gray Fog.
Just as the investigation records had described, they gradually lost their way among the mountain paths shrouded in Gray Fog. Unable to find the correct route up the mountain, they became trapped there.
Yet all the pilgrims maintained their unity and did not panic.
They hid in a mountain cave they had discovered by chance. By hunting the diseased animals in the mountains, they managed to survive, soon eating every animal in the back mountains.
As they ate the animals raw, their bodies also began to change without them realizing it.
Some pilgrims who deliberately ate the animals' eyes actually developed additional visual abilities. They could gradually see through the mountain fog and distinguish the correct path.
Moreover, they themselves began to crave eyeballs, and could even exert an "attraction" on other people's eyeballs from a distance.
However, the pilgrims maintained the foundation of their human nature. They did not forcibly take other people's eyeballs, but instead proposed the idea of a sole pilgrimage.
They would choose one person from among themselves and gather everyone's eyes in that person. That way, they could completely see through the fog surrounding the sacred mountain and complete the final ascent.
Ninety percent of the pilgrims, unable to see any hope of reaching the summit, were willing to offer up their eyes and let the sole pilgrim carry them to witness the pilgrimage's final scene.
However, the final candidate could not be decided directly, because ten percent of the pilgrims had already awakened abilities related to the eyes, and they all wanted to become that sole person.
After unanimous discussion, they decided to lock all of them in the mountain cave's secret chamber.