Eternal Darkness: Sanity's Requiem is a survival horror video game released for the GameCube. Developed by Silicon Knights and originally planned for the Nintendo 64, it was first released and published by Nintendo on June 24, 2002 in North America, October 25, 2002 in Japan and November 1, 2002 in Europe. It was the first video game published directly by Nintendo, rather than a third-party developer, to be rated M for mature by the Entertainment Software Rating Board.
Eternal Darkness' setting is centered around a mansion in Rhode Island - the home of protagonist Alexandra Roivas' grandfather - and a book that Alexandra finds there. It utilizes a third-person view in which the player must navigate a number of locations as twelve characters spanning different time periods. The game utilizes "sanity effects" to enhance the gameplay.
Though not a commercial success, Eternal Darkness was widely praised, winning the "Outstanding Achievement in Character or Story Development" award at the 6th Annual Interactive Achievement Awards, presented by the Academy of Interactive Arts & Sciences, and numerous other awards.
The plot of the game revolves around Alexandra Roivas, who is investigating the mysterious murder of her grandfather Edward Roivas. While exploring his Rhode Island mansion, she discovers a secret room containing, among other odd items, a book bound with human skin and bone. When she reads this book, The Tome of Eternal Darkness, she experiences a scene in the life of Pious Augustus, a respected Roman military commander in 26 BC. Pious is led by mysterious voices to an underground temple, where he chooses one of three mysterious artifacts. The artifact transforms him into an undead warlock, the Liche, and makes him slave to one of three Ancients, powerful godlike beings whose "Essences" are incarnated as the artifacts. As the plot unfolds, it becomes clear that Pious is attempting to summon his Ancient into this reality, while the powerful fourth "Corpse God" Mantorok is bound on Earth already, apparently helpless to stop it. If this summoning came to pass, the Ancient would feast on the bodies and souls of all living beings, and cast the universe into the horror of eternal darkness.
As she searches for and finds chapters of the Tome scattered throughout the mansion, Alex finds herself reliving the experiences of several (player controlled) individuals who have crossed paths with Pious or other servants of the Ancients over the centuries, and as a result came into contact with the Tome itself. While many of these individuals meet a sinister fate, their cooperation ultimately gathers the Essences of the three remaining Ancients in the mansion. Alexandra's own ancestors discover the long-deserted City of Ehn'gha beneath the family mansion, and powerful magickal machinery inside. Alexandra powers up this mechanism with the Ancients' essences, and summons a rival Ancient to fight Pious'.
While the two Ancients fight, Alexandra engages in combat with Pious with the aid of the spirits of his victims, the souls played in previous chapters, ultimately destroying his Ancient's essence. It loses the fight above as Alexandra kills Pious. Then, realizing that the Roivases and their allies have just brought another powerful ancient into the world, Edward's spirit quickly uses the mechanism in Ehn'gha to send the other Ancient back where it came from. He expresses pride in his granddaughter before he disappears.
After completing the game under all three alignments, it is revealed that all three Ancients have been destroyed — "All at once, separate and simultaneous, for the universe is made of many timestreams, many possibilities, all in harmonious synchronicity." Because he was bound, and not powerful enough to stop Pious Augustus himself, Mantorok manipulated the Roivas family into completing the work for him. He orchestrates the deaths of all three Ancients, in separate timestreams, and then connects them all, resulting in the annihilation of all three alignments. In the end, only the corpse god Mantorok is still alive, "festering in its tomb... plotting".