The cult was established following the Great Inundation of Mire's End, a catastrophic flood that claimed hundreds of lives forty years ago. As the waters receded, a woman named Elara Thorne emerged from the mud claiming the river had whispered the names of the dead back to her. She began gathering those who could not move past their grief, promising that the silt held the key to a true return. Over decades, the group transitioned from a support circle into a predatory organization that exploits the mourning to fuel their experiments with the 'Submerged Stream.'

The Sunken Sanctuary is a series of interconnected, half-submerged wooden chambers built into the thickest part of the reeds. It is perpetually damp, smelling of ozone and river rot, lit by bioluminescent algae.