Franken Stein of Soul Eater is a mad scientist hired to work as a teacher at DWMA early in the story.
Voiced by: Mitsuru Miyamoto (drama CD), Yūya Uchida (anime), Chuck Huber (English)
Franken Stein He views everything in the world as a specimen to be experimented on, including himself. He has a large screw sticking through the side of his head, and his skin and clothes are interweaved with stitches. He normally serves as a kindly father figure to his students, though he suffers from chronic bouts of madness that compel him to try and dissect anything in sight. Other than being a scientist, Stein is considered to be the most powerful meister to ever graduate from DWMA. He uses his Soul Perception ability to read his opponents' souls and use the data he acquires against them. He works well with many weapon partners, including his childhood partner and Lord Death's current weapon Spirit—who he experimented on in his sleep—and his old flame Marie Mjolnir. Even without a weapon, Stein is a master martial artist and can perform potent attacks with his soul wavelength alone.
Following Asura's resurrection, Stein's insanity worsens under the effects of the kishin's spreading madness wavelength to the point where Marie is assigned by Lord Death to be his weapon, her soothing soul wavelength quelling his insanity. However, he falls victim to Medusa's plans after she has Crona plant a magical snake inside Marie that worsens Stein's condition even more, though the snake is discovered by Joe Buttataki and removed. He is later framed for Joe's murder, but his companions refuse to believe he is the killer and allow him to evade arrest, eventually leading him to track down the true culprit, Justin Law. He is assigned as one of the participants in the battle between DWMA and Asura on the moon, where his madness is increased to such extremes that he begins to exhibit behavior not unlike that of a kishin.
In the anime adaptation, the snake in Marie's body is left undiscovered, driving Stein completely insane and causing to leave DWMA and join Medusa. He is later rescued by Maka, Crona, and Marie, the last of whom returns him to normal with her soul wavelength.