Chastel Aiheap serves as a knight in the Niren Brigade, fighting alongside her twin sister Hisca Aiheap, Yuri Lowell, and Flynn Scifo. Though identical to Hisca in features—sharing vibrant red hair and piercing yellow eyes—she is physically distinguished by a fuller figure. Her calm, gentle nature contrasts with Hisca’s stubbornness, reflecting their differing personalities.

Tasked with investigating erratic aer disturbances near Shizontania, Chastel engages in missions to disarm blastia traps and quell monster outbreaks. When an aer crisis threatens catastrophe, she joins Captain Niren Fedrok to enlist blastia expert Rita Mordio, securing a device to stabilize aer currents and avert blastia overload. Their efforts culminate in a decisive battle within a fortress harboring a rogue blastia core. As the blastia detonates, Niren sacrifices himself to save her, hurling her clear of the blast before vanishing in the aer’s surge.

Her dedication to the Niren Brigade underscores her loyalty and collaborative spirit within the team. Though absent from the original Xbox 360 release of the game, Chastel features in the PlayStation 3 version and Definitive Edition via a sidequest that delves deeper into her ties to the central story.