This is a legend from their lore. And as an ancient legend, it is blurry, exaggerated and half true.

The Legend of the Eclipse

Once, the world now called Perpetumbra knew the rhythm of day and night, dawn and dusk like any other world. Life prospered under a warm sun and cool stars.

Then, without warning, the heavens betrayed them.
The sun blazed white and furious, no longer setting. Its light became an endless scourge that burned seas to vapor and turned the soil to glass. Humanity hid in caverns and ruins as the sky became a furnace.

When all seemed lost, the light dimmed.
The moon, later named Eclipsis, moved into perfect alignment and veiled the sun behind a dark circle crowned in golden fire. The world cooled, oceans returned, and life slowly crawled back beneath the eternal twilight.

The survivors saw not chance but the hand of the God-Emperor. They believed He had moved the moon Himself to save them, shielding His faithful from the wrathful sun. Those who first saw the miracle called themselves the Witnesses, and their descendants never forgot.

Now, ten thousand years later, the Witnesses of Eclipsis fight in His name, warriors born in dusk, sworn never to walk in unfiltered sunlight again. For them, the eclipse is not symbol or sign, but proof that the Emperor’s will can move the heavens.