Divinity: Original Sin plot summary.
Plot edit
The customizable protagonists of the game are a pair of "Source Hunters": members of an order dedicated to the eradication of a dangerous magic named "the Source". 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 Source-related murder of a town councilor in Cyseal, a port town in southern Rivellon, which they find under siege by the orcs and undead. While looking for the murderer, they learn that the siege has been orchestrated by a conspiracy of "Sourcerers" (Source-users) linked to the Immaculates, a cult based in the Luculla Forest further inland. They also discover evidence that the so-called White Witch, guardian of the Luculla Forest, was the one who murdered the councilor. Their search for her eventually 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 admits to 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 a 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 to conquer Rivellon and powered by tenebrium and the Source. Before Leandra collapses the mines, the Source Hunters manage to recover her fail-safe that allows them to destroy the Death Knights.
Throughout the game, the Source Hunters occasionally encounter magical crystals known as "Star Stones" (some of them transformed into "blood stones" by the Immaculates' sacrifices). Upon finding the first one, they are transported to the "Homestead", a mysterious fortress outside of regular spacetime that is immediately familiar to both of them. As they recover more Star Stones, they learn from them that the Source had originally been a benevolent magic associated with Astarte, the goddess of life, before it was corrupted by the Void, an evil force from outside of the material world. The Source Hunters themselves are revealed to be reincarnations of two ancient generals, a man and a woman, who imprisoned the Source corruption inside an artifact known as "the Gold Box" and were granted godlike powers to guard it. However, a demonic being named "the Strife" persuaded Astarte to open the Box, releasing the corruption, which took the form of a giant dragon, which Astarte went on to battle for eternity in the Void. As penance for their failure, the Guardians chose to be stripped of their powers and memories and were reborn in Rivellon. Realizing that the Strife is now manipulating Leandra to weaken Astarte and to unleash the Void Dragon on the world, Icara urges the Source Hunters to stop her, either by restoring the psychic link between the sisters known as the "soulforge", or by killing her if necessary.
The Source Hunters follow the Conduit's trail to the town of Hunter's Edge near the Phantom Forest, now overrun by the Immaculates, orcs, and barbarian mercenaries. They find directions left behind by the wizard Zandalor, Icara's lover and Leandra's nemesis, that point them towards an ancient Source Temple hidden deeper in the woods. Inside the Temple, they find Zandalor and learn from him that Leandra's objective is the Gold Box in the First Garden, which they can enter from the Homestead. In the Garden, they confront Leandra and can restore her soulforge with Icara if they have unearthed the means thereof in the Phantom Forest earlier: in this case, she recognizes her own wickedness and leaves with Icara and Zandalor to repent; otherwise, they must fight and kill her. Reaching the Gold Box, the Source Hunters join forces with Astarte to destroy the Strife, but not before it summons the Void Dragon itself. After a titanic battle, they manage to banish the Dragon back into the Box, and Astarte stays to guard it again for all eternity, thanking the Source Hunters and revealing to them that other gods knowingly let the Source be corrupted. The Source Hunters then leave the First Garden to embark on a new adventure.