To fulfill a family promise, newly appointed Queen Evangeline pursues a demon who stole the mysterious blueprints and fled through a portal leading to the Underealm. While trapped, an ancient evil awakens in the darkness of the world beneath to unleash his fellow monsters upon the surface. As the Lightguardian battles for her life deep within Terwyndel's core, her companions face a new set of problems. Arthur struggles to maintain an unstable city during its reformation after the war. Sun must choose between her family's happiness and her own. Kerik is volatile under his own battle with humanity. The longer Eve is separated from her kingdom, the greater the chaos becomes within Tyrsfell. Will she be able to escape Underealm's vile clutches and stop the darkness from reaching the surface and its inhabitants in time?