"It seems that under Catherine's leadership, the rebels (or 'the Black Moiety' as the villagers obstinately insist on referring to them) have attained a new level of sophistication in their terror tactics, and have renewed their campaign to intimidate the villagers into joining them, playing upon their shared superstitions."
The Moiety were a group of Rivenese who opposed Gehn and his leadership of Riven. This group of rebels originated with two Rivenese who witnessed the confrontation between Gehn and Atrus at the Star Fissure, during which Atrus cast himself into the Fissure as he linked away, trapping Gehn on Riven. While not understanding the events fully, these two observers recognized that it was Atrus and Catherine who had trapped Gehn, and not, as Gehn would have them believe, he who had banished Atrus and Catherine. Their story spread, and the resistance against Gehn's rule was born.
Early History and Beliefs
In the early years of Gehn's entrapment, the Moiety considered seeking escape from Riven through the Fissure. While they were successful in solving the combination to the cover of the small window over the Fissure and noted the stop that prevented the telescope from breaking through, they ultimately decided against reopening the Fissure. However, this information was later used by the Stranger to contact Atrus after Catherine had been rescued from her prison.
The Moiety placed a high value on symbolism. Early on, they adopted the unique shape of the dagger situated at one end of the Fissure as a symbol of their cause and their representation of Catherine; defacement of this symbol was considered sacrilege. In later years, when they no longer feared discovery of their hideout, they would leave small copies of this dagger as calling cards. Unfortunately, Gehn used this value against them, using his crest and symbolic use of the Wahrk to invoke terror. Catherine would later try to dissuade them of the importance of symbols, but her efforts proved fruitless.
The Moiety's core doctrines were that Atrus, having imprisoned the false god Gehn, was a true god; that he had selected Catherine, the spiritually misfit Rivenese, to be his wife; and that Catherine was transcending into deity and would return to rule Riven forever. The details of Catherine's return were debated. Some expected her to overthrow Gehn, while others believed that she would lead the faithful on to a better existence.
When Catherine returned to Riven in 9461 DE (1806 CE), the Moiety, having been forced into hiding, lived in a complex series of caves which Gehn had yet to discover. They interfered with the surface only in superficial ways (and then always armed and in full regalia), stealing food, sabotaging Gehn's constructions, and sending out patrols. One of these patrols was fortunate enough to pass by the Fissure Plateau cage as Gehn's guard was inspecting Catherine's belongings, and they succeeded in darting him and carrying Catherine to safety. Over the next several weeks, Catherine learned of their beliefs and distorted accounts of her life and escape from Riven, but made no effort to undermine the foundation of their decision to resist Gehn. With the exception of her old friends, Eti and Nelah, few of the Moiety made efforts to become close to Catherine, causing her to sink into depression.
Upon learning that Gehn was making books and had succeeded in linking to another age, Catherine's view of her situation changed as she recognized the providence of her return. She discovered that the Moiety had possession of one of Gehn's failed test books, which had been partially written and burned, but was still mostly intact. She modified the book to write a new Age for her people, which contained a geode capable of powering Gehn's flawed book. She succeeded in evacuating all the Moiety to Tay, thus fulfilling their prophecies. She considered destroying Tay's Descriptive Book in order to safeguard her people, but was captured by Gehn before she was able to enact this plan. The book was subsequently stored in the Moiety Gateway, presumably to allow the Moiety to assist Atrus when he came to rescue his wife.
Events of Riven
In spite of her imprisonment, Catherine was able to maintain contact with the Moiety through Nelah, who was able to gain Gehn's trust and serve as a double agent. It was through this contact that she learned of the arrival of the Stranger in 9462 DE (1807 CE); once again, the Moiety, on watch for Atrus, had succeeded in overcoming Gehn's guard, stealing the Prison Book and setting the Stranger free. Working through Nelah, Catherine ordered the return of the Prison Book, sending her journal and a note along with it to fill the Stranger in on the events since her arrival. When the Stranger arrived on Tay, s/he was taken captive but later allowed to return to Riven in order to trap Gehn.
Following Gehn's entrapment, Catherine was freed from her prison and succeeded in evacuating the remaining villagers to Tay before meeting with the Stranger and Atrus at the Star Fissure. It is unclear what became of the Moiety after the events of Riven, but it is likely that with threat of Gehn past them, Catherine disbanded their cult and attempted to correct their false beliefs concerning Atrus and herself.