Lestion, known also as Leon, is a dream demon consumed by vengeance against Mistleteinn, the powerful dream demon who slaughtered his comrades. He manifests with a distinctive cowboy-like appearance, typically wearing a large hat that shadows his face, and wields mounted guns on his arms firing blue bullets. His personality radiates cold determination and unwavering focus on revenge, showing no concern for collateral damage or necessary sacrifices. He partners with a human vessel, Chizuru Kawanami, whose emotional detachment and resignation make her compatible for his mission in the real world. Lestion explicitly states they seek no allies beyond their shared purpose of retribution.

His history centers on repeated, devastating battles against Mistleteinn where all his fellow dream demons perished. He alone survived these encounters, fueling his obsession to destroy her. For the final confrontation, he wields a specialized gun designed specifically to kill Mistleteinn, though using it demands a fatal cost. Its ammunition consists of the despair and agony of deceased dream demons, while Lestion himself functions as the gunpowder; firing the weapon would consume and kill him. During their climactic battle, he wounds Mistleteinn—marking the first known instance of injuring her—but is ultimately killed. His death fulfills his role in the conflict without achieving his ultimate goal of eliminating her.