Eternal Darkness: Sanity's Requiem is an action-horror game with a third-person view. The game's story narrative switches between two phases. The main phase focuses on a series of chapters in which players take control of a new character each time. The other phase acts as an intermission. The game features twelve playable characters, split between four different locations and from different time periods. Each of them differs in the game's three main parameters — health, sanity and magic — and has access to a small selection of weapons that they can use in combat, although what they can use is determined by the time period or era in which they lived. For example, characters from more ancient eras are limited primarily to melee weapons such as swords, with the occasional crossbow or thrown weapon.