Based on the given passage tell me who masked cultists are?

Context: Aloy is cast out from the Nora tribe at birth and raised by a fellow outcast named Rost. As a child, Aloy obtains a Focus, an augmented reality device that gives her special perceptive abilities. Aloy becomes curious about her origins and is told by Rost that if she wins the Proving, a competition to earn the right to become a member of the Nora, the tribe's Matriarchs might concede this information. Aloy spends some years training in combat and survival under Rost's instruction. After coming of age, Aloy participates in the Proving; she wins the competition, but masked cultists attack the Nora. Rost sacrifices himself to save Aloy from their leader, Helis. When Aloy awakens, the Matriarchs explain that Aloy was found as an infant before a sealed door within the Nora's sacred mountain and that these suspicious origins were the reason for her being an outcast. The Matriarchs name Aloy a "Seeker," allowing her to leave their lands in pursuit of the cultists. Aloy eventually learns that the cultists are part of a splinter Carja faction called the Eclipse and that Aloy was targeted due to her resemblance to an Old World scientist named Elisabet Sobeck. Aloy locates the ruined corporate campus of Faro Automated Solutions and discovers that the Old World was destroyed nearly a thousand years ago after Faro lost control of its automated peacekeeper military robots. The robots, which could self-replicate and consume biomass, overran the planet and engulfed the biosphere, stripping Earth of life. Zero Dawn, a project spearheaded by Sobeck, was initiated to create an automated terraforming system to deactivate the robots and restore life to Earth.

Answer: The masked cultists attacked the Nora when Aloy won the proving competition. Their leader was named Helis. The cultists were part of a splinter Carja faction called the Eclipse and wanted to kill Aloy due to her resemblance to an Old World scientist named Elisabet Sobeck.