Birthright takes place before the games Diablo and Diablo II take place. It tells the story of Uldyssian ul-Diomed, a farmer whose only remaining family is his brother, Mendeln. Initially the story starts out with some background information. Uldyssian's family falls victims to a plague, which only he and his brother survive. Not too far into the novel, a terrible murder is unearthed in the woods near his home village, Seram. In this time he has already become infatuated with a stranger to the town named Lylia, and he has started to possess eerie powers, like a thunderstorm that left many dead, including the men of the Cathedral of Light who accused him of the murder and were there to arrest him. Uldyssian and Lylia, along with Uldyssian's brother Mendeln, a woman from their village named Serenthia, and a skilled hunter named Achilios, escape under cover of the storm for the nearby forests. Once there, Lylia explains to Uldyssian that his power is a gift and he accepts this, and comes to awaken the same power in Serenthia and Achilios. Not long after their escape, they are set upon by Peace Warders and a priest from the Temple of the Triune, which stands in opposition to the Cathedral of Light, but Uldyssian easily routs them with the help of Lylia and they continue on to her desired destination. Meanwhile, the priest of the Triune who led the attack against Uldyssian—Malic—returns to the Primus of the Triune, Lucion, who tortures him for his failure. The torture ends with Lucion's gifting Malic with a demonic arm and several vicious morlu to aid his second chance at capturing Uldyssian and bringing him back to the main Temple.