Alastor is the Crimson God of the Crimson Realm, known as the Flame of Heaven and the God of Retribution. He is bound by contract to the Flame Haze Shana, expressing his will through a divine vessel called Cocytus, which takes the form of a black pendant she wears around her neck. His true appearance is that of a massive, minotaur-like creature with powerful limbs, large wings like the night sky, and burning eyes, his entire body shrouded in flames capable of incinerating everything in his path. Feared among Denizens as a god who can kill other gods, he is considered one of the mightiest beings in existence. His primary motivation is to maintain the balance of the world by preventing Denizens from consuming the Power of Existence from humans. Alastor’s personality is regal, wise, and solemn, befitting his divine status. He serves as a stern but caring father figure to Shana, having watched over her since childhood and deeply protecting her, even manifesting his true form to annihilate enemies who gravely wound her. Despite his serious nature, he can be awkward when dealing with unfamiliar human concepts like relationships or reproduction, a trait for which he is gently chided by close associates. He shares a significant history with his previous contractor, Mathilde Saint-Omer, whom he loved; she perished summoning him during the Great War using the divine summoning technique known as Tenpa Jōsai, or Heaven-and-Earth Sundering. This ability manifests his true form and burns everything to ashes, typically at the cost of the contractor’s life, though Shana is the first to survive it. Alastor also possesses an Unrestricted Spell called Tatsui no Gen, the Speech of Conveying, which allows him to read the intentions of others. His relationship with Shana evolves from a master-contractor dynamic into a profound father-daughter bond. With Yuji Sakai, he is initially cold and critical, viewing him as a distraction, but over time he grows to trust him as a valued ally, though he rarely shows it openly. Throughout the series, Alastor learns from his own mistakes, acknowledging that he and others focused too much on Shana’s combat training while neglecting her social and emotional growth. His perspective broadens as he comes to understand the importance of human bonds and emotions, evolving from a distant, judgmental force into a guardian who supports Shana’s growth and independence.