Rift

Origin: Abyss of the Horizon
Area Affected: Kuze Shrine/Dreams of Tattooed Curse victims
Associated Disaster: The Unleashing
Notable People Affected: Reika Kuze, Yashuu Kuze, Handmaidens, Shrine Carpenters, Tattooed Curse victims
In Fatal Frame III, the Rift is the infernal force that must be subjugated by performing special rituals. In the game, the Rift is considered to be both the physical and the metaphysical gap between the living and the dead. The physical rift is located deep under the Kuze Shrine, and is the body of water that separates the Abyss of the Horizon from the rest of the Last Passage, where the dead cross over to the other side. The metaphysical Rift exists in this same area, and was contained in the Chamber of Thorns. In the vernacular of those living in the Mutsu region, the word "Rift" is also used as a synonym for dreams. Much like the physical rift, these dreams, arising from love for the dead, traverse the border between the world of the living and the afterlife. When a person dreams frequently of lost loved ones, and of the pain of loss, their dreams become a gateway for the dead to return. Therefore, people would come to offer their pain to the Tattooed Priestess, who could sleep forever and so keep the Rift within dreams.
However, when Reika Kuze's eyes were tattooed, the pain of the Holly was reflected back out into the world. Those consumed by the physical Rift while it was spreading felt great pain, as it spreads slowly. They would also be covered with tattoos, as in the cases of Yashuu Kuze and the Engraved Men.
Much like the portals to the underworld in the previous games, the Rift must be kept from expanding by offering human sacrifices. Ideally this would mean sending the restless priestess in a boat as an offering to the "other side." The Priestess, bearing the pain of survivors, must endure in the "Hell of Holly" for all time. After Reika released the Rift, however, it spread from deep within the Last Passage into the Kuze Shrine, and prevented anyone from getting near enough to perform the sending off.
Instead, sacrifices of Shrine Carpenters and Handmaidens were made at various points all around the house, to keep the Rift contained. The first to be sacrificed was Amane Kuze at the bottom of the Abyss, near the Chamber of Thorns. The Rift spread gradually, allowing time to summon Shrine Carpenters in secret, to build onto the Manor, and then to be sacrificed and buried within the walls. The completed structure was sealed within a dream, so that the awakened Priestess could wander in her dream-like state for all eternity without the Rift spreading.
Because of Reika's desire to share her pain, those who were constantly dreaming and thinking about dead loved ones still invited the Rift into the real world, and were drawn into the Manor of Sleep in their dreams. They would eventually succumb to the Tattooed Curse. They became more vulnerable if they visited the real-world Kuze Shrine, or if another Tattooed Curse victim dreamed of them.
When Rei Kurosawa was able to send Reika off in the boat, the Tattooed Curse was lifted, the dead were able to pass on, and the Rift was contained.