The illness first appeared in the dense forests of Eirendor, near the small elven settlement of Lathirin. Its source was never established. Some blamed an ancient curse buried in the roots of the great trees of Eiryn Downs; others believed it emerged from a tear between the planes where shadow and light meet. The earliest signs were subtle: a dimming of the sun over Lathirin, a silence that settled over the land, and a faint mist that lingered even at midday.

The plague ran in two stages. In the first, the Twilight Onset, victims felt a creeping chill and saw the world as if under perpetual dusk. This stage lasted days to weeks, marked by disorientation, paranoia, and a compulsion to avoid light. Some reported whispers or flickering shadowy figures at the edge of sight. In the second stage, the Eternal Night, victims fell into an unending coma, trapped in their own minds in a realm of perpetual twilight where phantoms and dark creatures hunted them. Attempts to wake the afflicted often killed them, and magical healing was ineffective or produced unpredictable, tragic results.

The plague spread quickly across Eirendor, carried on the wind and leaping from one community to the next. Villages were quarantined. Many believed it was divine punishment or a dark spell, and rumors spread of shadow cults and forbidden magic. Healers, mages, and clerics from across Eldranis worked to find a cure, but for nearly twenty years the illness defied them all.

The breakthrough came from an unlikely alliance. Eleneth, a rogue elven mage exiled from Eirendor for experimenting with forbidden shadow magic, joined Father Ilyn, a human cleric of Aurelios. Together they devised a ritual that drew on both light and shadow to open a bridge into the dream realm where the victims were trapped. A great assembly of priests, mages, and druids gathered at the sacred grove of Amarael.

The ritual took three nights. On the first, the assembly endured attacks from creatures of shadow. On the second, they faced the victims' own nightmares pulled into the waking world. On the third night, Eleneth and Father Ilyn vanished into the twilight, and with the final incantation the plague's grip broke. The victims woke, and the curse over Eirendor lifted. Neither Eleneth nor Father Ilyn was ever seen again, and both were honored as heroes.

Some regions stayed permanently touched by shadow and became known as the Gloaming Woods. Many who woke were changed for good: some could see in darkness or glimpsed future events in their dreams, while others were left haunted by lingering fears. The ritual that ended the plague became an annual observance across Eirendor.