Rain of a Thousand Stars
The Rain of a Thousand Stars refers to a series of events durning the Primordial War, beginning as that conflict transitioned into direct confrontation between the Exalted and the Primoridals and ending with the consolidation following their defeat. While the vast majority of the Celestial Bureaucracy backed the efforts of the Incarnae to overthrow their creators, not-insignificant minorities took a neutral stance or supported the Primordials.
The Unconquered Sun, perhaps eager to crush those who defied his power, perhaps driven to remove those whose agendas threatened the Creation he existed to defend, brooked no such defiance: after the victory of the Incarnae, the gods on the losing side were purged and replaced with loyalists, and even before this certain gods were targeted by direct attack or charges of failing in their duties in the Celestial Bureaucracy (which Sol Invictus held to include obedience to the Most High). There was little mercy to be found, those gods removed from their posts, fleeing Creation, suffering permanent imprisonment, or being smelted into Starmetal... Yu Shan considers this process to have been complete, though those who move through the darkest corners of Creation sometimes whisper at least a few such spirits still persist as the vengeful Forbidden Gods.
Regardless of the methods used in their removal, the battles against and purges of gods loyal to the Primordials are known collectively as the Rain of a Thousand Stars. The gods themselves rarely mention such discomforting events, the term seeing more use amongst the Sidereal Exalted, it being the origin of many of their most ancient Artifacts.