TV-Series
Description
Marie Mjolnir is a Death Scythe, one of the elite demon weapons created by Lord Death, originally assigned as the Death Scythe of Oceania. She later returns to the Death Weapon Meister Academy after the escape of the Kishin Asura, taking on the roles of instructor and partner to Doctor Franken Stein. Her background includes a period of uncertainty following her ascension to Death Scythe status, during which she considered retirement and chose the Oceania post primarily because of its light workload, hoping it would give her time to find a romantic partner and settle down.

Personality-wise, Marie appears carefree and often absent-minded, with a notably poor sense of direction that causes her to get lost easily within the Academy. Beneath this exterior, she carries deep insecurities about her personal life. She has experienced a string of failed relationships, including with Joe Buttataki and with Franken Stein, for whom she still harbors lingering feelings. Her longing for marriage and family is strong, and she has even been known to express desperation on the subject. Despite these vulnerabilities, she is a genuinely caring person who shows warmth toward others, especially the students. She pushes her unfulfilled desire for motherhood into her teaching, spending time with students outside the classroom and helping them with personal matters.

Her motivations are shaped by both duty and personal need. She accepted her reassignment and partnership with Stein not only because Lord Death ordered it but also because she cares about Stein and hopes to help counter the influence of Asura that threatens his sanity. She also takes her role as an instructor seriously, assisting in making the transition of the troubled student Crona into the Academy more bearable.

In the story, Marie serves as a supporting character who appears after the early arcs. She is summoned alongside the other Death Scythes—Yumi Azusa and Justin Law—in response to Asura's resurrection. Thereafter she becomes a faculty member at the DWMA and a constant presence in Stein's life, both as his weapon partner and as his emotional anchor. Her combat contributions are significant when she fights alongside Stein, using her formidable strength as a weapon.

Her key relationships center on Franken Stein, her meister and former crush; Azusa and Justin Law, fellow Death Scythes; and Lord Death, who commands her. She also interacts with the main student cast, particularly Crona, whom she helps adjust. Her relationship with Stein evolves from an old crush into a working partnership and eventually a marriage in the manga continuity.

In terms of development, Marie grows from a dejected, romance-obsessed weapon who once considered giving up her career into a capable instructor and a reliable ally. She learns to balance her personal desires with her responsibilities and becomes more confident in her role, though her absent-minded and lovelorn traits remain part of her character.

Notable abilities include her extreme physical strength even in human form. Her weapon form varies between adaptations: in the anime, she transforms into a large gray tonfa; in the manga, she initially takes the form of a small black hammer that can reshape into a tonfa, with the length of the tonfa increasing in proportion to her wielder's soul wavelength. In both versions, the weapon bears the lightning-bolt symbol that also appears on her eyepatch. She can perform Soul Resonance with her meister to amplify their combined power for devastating techniques. She has also been shown using unconventional tactics, such as throwing her weapon form like a boomerang to strike enemies at range.