As the Holy Empire tightens its grip on neighboring territories, the peaceful island of Erin, inhabited by the Gael tribe, becomes its next target. When the priestess Riannon is taken captive to be sacrificed to the dreaded demon king Arawn, her brother Arthur, the tribe's valiant warrior, comes to her rescue. To their surprise, Arawn appears not as a malevolent force but as a charming silver-haired man. Concealing his ominous past, Arawn allies himself with the Gael tribe, offering his strength and guidance. Together with a diverse group of companions—a skilled swordsman, nimble hunter, and mischievous pixies—they unite to challenge the Empire's oppression, all while unearthing the hidden truths shrouding their world.