The Void Nights were a period from 4E 98 to 4E 100 when Nirn's two moons, Masser and Secunda, vanished. This caused great confusion across Tamriel, and became a crucial step in the build up to the Great War. While most of the Empire viewed the Void Nights with trepidation and fear, in Elsweyr it was far worse. Culturally, and biologically, the moons are much more influential to the Khajiit, as the phases of the moons determine which breed a Khajiit will be. After two years, the Thalmor announced that they had restored the moons using previously unknown Dawn Magicks, and the moons returned, but it is unclear if they truly restored the moons or just took advantage of foreknowledge that they would return.
Regardless of the truth of the matter, the Khajiit credited the Thalmor as their saviors. Within fifteen years, Imperial influence in Elsweyr had so diminished that the Empire was unable to respond effectively to the coup of 4E 115 which dissolved the Elsweyr Confederacy and recreated the ancient kingdoms of Anequina and Pelletine as client states of the Aldmeri Dominion.