With the emergence of the Holy Empire comes the gradual absorption of neighboring lands, including Erin, a small island inhabited by the Gael tribe. Rumors swirl about the demon king Arawn, who allegedly caused a great deal of destruction, and Riannon, a priestess, has been kidnapped as a sacrifice to the demon. Thankfully, First Warrior Arthur, Riannon's brother, rescues her from the grasp of the Empire. However, their escape is cut short by the sudden appearance of Arawn, who poses as an amiable, silver-haired man. Arawn pledges his loyalty to the tribe's cause and fights alongside Arthur and his group, consisting of a skilled swordsman, an agile hunter, and a pack of gleeful pixies, as they battle the Empire. Through their journey, the group uncovers the land's sinister secrets while Arawn remains enigmatic and hides his true identity.