Sitonai exists as an Alter Ego-class High-Servant and Pseudo-Servant, emerging from the fusion of three mythological entities: the Ainu dragon-slaying heroine Sitonai, the Norse goddess of love and war Freyja, and the Finnish ice-witch ruler Louhi. This triad inhabits the vessel of Illyasviel von Einzbern—a homunculus crafted by the Einzbern family as a Master candidate and Lesser Grail—united by shared themes of sacrifice, fascination with youth, and dominion over frozen realms. Her personality mirrors Illyasviel’s outwardly cheerful innocence, layered with Sitonai’s valor against annihilation, Freyja’s compassionate insight, and Louhi’s icy pragmatism. This blend of contrasting traits surfaces in her interactions: warm camaraderie with allies juxtaposed with dispassionate precision in battle. Within the Scandinavian Lostbelt, she operates as Scáthach-Skadi’s captive, capitalizing on her bond with the protagonist to forge tactical coalitions. Her capabilities include summoning Heracles, whose primal guardianship echoes Illyasviel’s history, and dissecting anomalies in Servant Spirit Origins to pinpoint objectives such as the Fantasy Tree. Interpersonal dynamics reflect fragmented echoes of Illyasviel’s memories, sparking tense exchanges with figures like EMIYA (Assassin) and Heracles. She openly distrusts Gilgamesh yet harbors measured interest in his Caster incarnation, while silent reverence for Irisviel (Dress of Heaven) lingers beneath unspoken emotional complexities. Visual design elements—silver hair, frost-themed garb, and fur-lined accessories—underscore her affinity for wintry domains and composite divinity. Though her narrative remains anchored to *Fate/Grand Order*, a brief appearance in *Fate/Grand Carnival*’s opening theme preserves her core aesthetic and mythological coherence without expanding her established role.