The Watershed was an event that occurred in 4100 CGC in the Ealdremen System wherein the inhabitants of the system waged open war on the serpentine verge god known as 51-8: Coil, which existed at the known edges of the solar system and seemingly barred the increasingly advanced civilizations of Ealdremen from ever discovering what laid beyond. As then-modern understanding of verge gods and their potential negative influence on real space developed, groups such as the Iconoclasts stepped to the forefront of the public eye with promises of liberation. Armed with weapons and spells since scattered and lost with the end of the Millennial Calm, the Iconoclasts and their allies tracked several verge gods and attempted to slay them. 01-4: Lambency was one such casualty, and the more powerful verge gods 48-5: Pursuer and 51-8: Coil were also targets of the near-simultaneous attacks.
The half-death, attempted murder, or otherwise attack on 48-5: Pursuer is often thought to be linked to the Valtheri Sequence-XX Extinction, an ongoing phenomenon that has led to the valtheri species approaching extinction in the hundreds of years since the Watershed. However, it is the attack on 51-8: Coil that is generally at the forefront of discussions of the Watershed, as the breaking of 51-8: Coil's body is said to have rained scales down upon every planetary surface throughout Ealdremen. This "storm of godfire" laid waste to cities and natural geography alike, and it even broke open the planet Mioura and scattered its pieces. While it is impossible to know the true number of casualties from the Watershed itself, population censuses before and after the Watershed have differences of millions on planets "less affected" by the event, and it is estimated that Mioura's population of about 1.5 billion people perished with few exceptions from the planet's destruction.
The Watershed is generally regarded as the definitive end point of the Millennial Calm, for the event set back Ealdremen's advancements in all forms of society and science, and the years since the Watershed have been dominated by threats of war that were realized in 4340 CGC with the Chrono Stars War.