The customizable protagonists of the game are a pair of “Source Hunters”: members of an organization dedicated to eradicating a dangerous magic named “the Source” and its adepts, the “Sourcerers”. In the single-player mode, the player controls them both, while in the two-player co-op, each player takes control over one of them. At the start of the game, the Source Hunters receive orders to investigate the murder of a town councilor by a suspected Sourcerer in Cyseal, a port town in southern Rivellon. Upon arrival, they find Cyseal under siege by orcs and undead and soon discover that it was orchestrated by a Sourcerer conspiracy linked to the Immaculates, a cult based in the Luculla Forest further inland. They also find evidence implicating the White Witch, guardian of the Luculla Forest, in the murder. Their search for her takes them to the fairy realm of Hibernheim, where they find her trapped in a block of ice by the Immaculates’ leader, the Conduit. Upon being freed, she introduces herself as Icara and pleads guilty of accidentally killing the councilor, but the Source Hunters, having uncovered evidence of Sourcery, mass murder, and human sacrifice carried out by the Immaculates, choose to ally themselves with her against the common foe. Icara reveals to them that the Conduit is actually her own estranged sister Leandra and directs them to infiltrate the Immaculates to learn of her plans. The Source Hunters discover that the cult has been mining a highly toxic metal named “tenebrium” in the Luculla Mines, where they also encounter “Death Knights”, indestructible undead warriors created by Leandra using tenebrium and the Source to conquer Rivellon. Leandra destroys the mines in an attempt to kill the Source Hunters, but they manage to escape with her fail-safe that renders Death Knights vulnerable.