The Slow Coil is the Yuan-ti name for the swamp plague that drove them west. It begins quietly: a dusk fever that comes and goes, a heaviness in the limbs as if the body were filling with silt, dreams that drag like wading through reeds. Weeks turn to months. Muscles knot and tremble, scales pit or flake in uneven patches, and the breath takes on a faint marsh-sweetness. Victims tire after a few dozen paces; sleep gives little back. In wet places the sickness tightens—night sweats rise, joints throb, and the world tilts as if on soft mud. In the dry, it loosens its grip, never gone, just… less.
Signs are there if you know them, but none are certain alone. Purebloods show light-sore eyes and a metallic taste they can’t shake; Malisons ride hotter fevers and rough, uneven sheds; Abominations carry clouded eyes and scarred plates but often stay on their feet. A ring of pale scales at the throat, a pulse that stutters at sundown, fingers that won’t quite stop shaking—these are the tells yuan-ti watch for when they tie a new knot in the cairn rope. They boil water, salt their food, burn reed bundles to clear the air, and keep a quarantine rope between themselves and the curious. Outsiders argue about how it travels—bad wells, breath, curses—but the The Great Migration moves on, slow as its weakest, following dry wind and rumor toward any place that might ease the Coil’s grip.