Eternal Darkness: Sanity's Requiem is a horror/adventure video game developed by Silicon Knights for the Nintendo GameCube console. The game allows players to play as various different characters throughout time, all of whom run afoul of a conspiracy to revive one of three ancient evil demigods from its sleep. The game adds an innovative function in its use of a sanity meter, similar to a life meter, which is depleted when the player character witnesses or experiences something particularly disturbing. The character is increasingly likely to hallucinate as the sanity meter drops; hallucinations manifest as enemies who disappear, snippets of gameplay that reset to where the game was a few moments before, and in other novel ways.