The Eclipse (also known as Eclipse Cultists) is a multi-tribe cult predominately made up of and currently led by Shadow Carja members. The Eclipse seek to use the machines to wipe out the other tribes and restore the Shadow Carja to their perceived rightful place in Meridian.
The Eclipse was founded by Sylens in order to use its Shadow Carja followers to serve Hades' own ends. The Shadow-Carja were chosen to form Eclipse due to them being easily manipulated through religion and nationalism following their defeat in the Carja civil war, and were made into believing Hades was the "Buried Shadow" god from Carja mythology. They follow Hades in the belief that it will help them to control the machines, and plan to use them to retake Meridian and conquer the world. But, they remain unaware of Hades' true intentions: to reawaken the Faro Plague and destroy the world once again. Sylens was forced to flee from the Eclipse after learning Hades had no use for him and had marked him for death. The Shadow-Carja champion Helis replaced Sylens as Hades's trusted follower.
The Eclipse kept their existence unknown to the world, killing any witnesses. The cultists explore Old One ruins and dig up and reactivate Faro machines, which they use to infect and control other machines.
Some years later, Hades ordered Eclipse to kill the Nora warrior Aloy, whom Hades deemed her as a threat to Eclipse's so-called god. The cultists led by Helis attacked the Nora during The Proving. Despite killing many Nora in their carnage, they failed to kill Aloy. This event, however, forced Aloy into a personal war against Eclipse. After Aloy foiled Eclipse's operations during her journey, the Eclipse eventually captured her at their capital city of Sunfall and thrown her into the Sun-Ring. But she was only to be saved by Sylens, who have been aiding her to foil Eclipse and Hades's goals.
Eclipse ultimately launched a full-scale assault on Meridian with their armies of corrupted machines, and Hades being directly taken to the Spire in order to use it to transmit its signal to awaken the Faro Plague. The defenders of Meridian - Carja, Oseram, Nora, and Banuk alike - fiercely defended the city. The battle resolutely ended in Eclipse's defeat: Helis lose his life at the hands of Aloy, who then managed to stop Hades's signal from destroying the world.