Soul Sacrifice is a brutal combat experience where every decision made will have consequential results.
The main protagonist of Soul Sacrifice is one of the innocent bystanders that has been enslaved by a powerful and cruel sorcerer known as Magusar, who absorbs human sacrifices to remain immortal. Just before the protagonist is going to be sacrificed, a talking book appears before them. The book, named Librom, is a collection of stories that describe past fights between monsters and the powerful sorcerer. The player character is able to enter the book's world and experience the fights in events known as Phantom Quests, thereby gaining the experience and power needed to defeat Magusar.

The game has two endings depending on whether the player saves or sacrifices Magusar after his defeat. There is also a third ending that occurs if the player defeats Magusar before completing all of the main stories in Librom.