Dr. Heinrich "Heinz" Schneider, a German immigrant physicist with no family, was wholly devoted to his scientific work. He served as the principal scientist for Project Leviathan, an initiative researching the artificial revival of ancient witch capabilities. Schneider held direct responsibility for the care, development, and study of Ellis, a young subject engineered with witch DNA intended to manifest powers like thermal manipulation and levitation.

Initially detached and professional toward Ellis, Schneider's attitude evolved. He began to genuinely care for her well-being, fueled by growing suspicions about project director Douglas Rosenberg's true motives and increasingly cruel methods to force Ellis' powers. Witnessing Ellis' distress during testing, Schneider eased the experiments and introduced her to the outside world, fostering a bond where Ellis developed deep affection for him.

Convinced of Rosenberg's dangerous intentions, Schneider resolved to escape the project facility with Ellis. During their farewell celebration—a Thanksgiving dinner at the Winchester mansion—Rosenberg intervened, fatally shooting Schneider through an open window as Ellis stood nearby. With his dying words, Schneider urged Ellis to flee. His murder became the catalyst for Ellis' amnesia and subsequent journey.

Schneider's death profoundly impacted Ellis, who carried guilt under the mistaken belief she caused it. His ghost later appeared to Ellis after her resurrection at Wiñay Marka, expressing gratitude toward her before vanishing.