Fallen Legion Revenants is a turn-based strategy role-playing game with turn-based combat and visual novel elements in a fantasy setting. In a world covered in deadly miasma, the floating castle is the last refuge for humanity. The land is filled with bloodthirsty monsters mutated by the plague, while Velkin Castle is in quarantine. Lucien, a charismatic politician sheltered within the castle walls, discovers an ancient book. She told about the Samples — weapons that can heal the world. Lucien joins forces with Rowena to overthrow the mad tyrant who controls the castle.