Reinhard Tristan Eugen Heydrich, also known by the demon name Mephistopheles, serves as the leader of the Longinus Dreizehn Orden and the primary antagonist. Born as the Apoptosis of the Mercurial Snake, he possessed a soul of exceptionally high quality from birth, which granted him superhuman abilities and an innate Sense of Foreknowledge. This sense produced a constant feeling of déjà vu and the perception that all experiences had been lived before, rendering his life devoid of challenge or joy. He initially displayed a cold and emotionless personality, earning the title "The Man with the Iron Heart." He lived an empty existence, excelling perfectly at everything without effort, leaving him perpetually unsatisfied and craving something unknown. After extensive interactions with Mercurius and undergoing an awakening, his personality shifted. He became highly philosophical, charismatic, and addicted to combat, seeking opponents who could challenge him on equal terms. He developed a deep love for the world and all its inhabitants, though he equated love with destruction, viewing the annihilation of the universe as the ultimate act of love. He values loyalty, honor, and freedom, with a core goal of ending destiny to make all experiences new and unknown. His relationships are complex. He shares a unique bond with Mercurius, considering him a sworn friend and the only being he does not hate. He has a son, Isaak, born from Lisa Brenner, but he refuses to acknowledge paternity, referring to Isaak as an abomination. Despite this, he extends the same impartial love to Isaak that he holds for all existence. His background includes a high-ranking position in Nazi Germany, where he interrogated the mage Karl Kraft after Kraft predicted an assassination attempt on Hitler. This encounter led him to form the Longinus Dreizehn Orden. During a confrontation, he effortlessly defeated Eleonore von Wittenburg, Beatrice Waltrud von Kircheisen, Wolfgang Schreiber, and Wilhelm Ehrenburg after ceasing to hold back his powers, fully awakening his Sense of Foreknowledge. He later faked his death to pursue godhood away from the German Army. The first Transmutation of Gold ritual during the burning of Berlin failed, causing his soul to ascend to Gladsheimr while his physical body remained on Earth. In the events preceding Kajiri Kamui Kagura, the god Hajun ascends to the Throne and kills Marie and Mercurius. Their deaths cause him, as an Apoptosis, to cease existing. His abilities are vast due to his status as an Apoptosis of Mercurius. He possesses immense superhuman strength, immortality tied to Mercurius's own desire for death, and regeneration. The Sense of Foreknowledge allows him subconscious access to memories from past timeline iterations. He commands a legion of souls with far greater power than any other Longinus Dreizehn Orden member, and his own flesh serves as the Holy Relic Heilige Eohl, offering impregnable defense with anti-physical, anti-magical, anti-temporal, and anti-accident properties. His primary weapon is the Longinuslanze Testament, a holy lance that always hits its target, is always faster than its target, and erases its target from existence. Merely looking at it can destroy the souls of most beings. His Briah, Gladsheimr - Gullinkambi Fünfte Weltall, manifests as a golden castle where the Obsidian Round Table resides, allowing him to resurrect and access all abilities of his legion. As a Hegemony God, his law, Du Sollst - Dies Irae, raises his entire legion to his level, turning them into Pseudo-Gods under his command. He is revived along with other Hegemony Gods by Naraka for a mysterious purpose in the Dies Irae Pantheon.