The Prophecy of Light was foretold by the Chozo that inhabited Tallon IV. The Chozo that wielded the distant sight foretold the coming of a Worm in a meteor, carrying a Great Poison with it. This event came to pass, and they built a Cradle to contain the poison, though it would ultimately prove unsuccessful. The Chozo left for an unknown destination, leaving behind weapons and upgrades for the use of an Entrusted One to fulfill the prophecy of breaching the Cradle and destroying the Worm.
"Chozo script translated.
Throughout our living nightmare, as we battle with this unyielding darkness, we Chozo see a light. This light glows with promise, chasing the shadows cast by the Great Poison and purifying that which has grown toxic. It is strange, though - at times it looks to our eyes as if the light coalesces into the figure of a woman. Burning brightly, the luminescence descends from space then retreats back into the infinite blackness from whence it came. When this prophecy comes to pass, when the light recedes, the Chozo's long vigilance of containment will finally come to an end."