Magatsuhi (マガツヒ, kanji: 禍霊, literally "Spirit of Calamity") in Shin Megami Tensei III: Nocturne is a very important substance in the Vortex World. It is visualized as flowing red strands of energy, or a shining red liquid if allowed to pool. It affects the summoning, strength, and sustenance of demons, serving as a power medium. A large amount of Magatsuhi is also necessary to summon a Demonic Sponsor to support a Reason.
It is born from the flow of strong emotions and humans have an abundance of it, especially when they are in a panicked or fearful state. Manikins, counterfeit humans born from the emotions of multiple spirits, are also a source of Magatsuhi. It's implied almost every human being outside of the Shinjuku Hygienic Hospital at the moment of the Conception was reduced to Magatsuhi and drawn into the Vortex World, the remainder reduced to empty spirits. Pooled Magatsuhi can also settle in the earth to create Manikins.
Thor was seen violently draining Isamu Nitta of his Magatsuhi in the Mantra Army HQ, indicating this was the routine way of extracting the substance from living entities, similar to the torture the Manikins underwent when imprisoned in Kabukicho Prison.
The majority of the facilities in the Vortex World are powered by Magatsuhi. In fact, the Amala Network itself transmits matter between Amala Drum Terminals (in a two-way manner between large to large drums or a one-way manner from small to large drums) by merging solid states along Magatsuhi flow lines and moving them to the specified destination terminal in an instant.
The concentration of Magatsuhi is far from uniform, and a number of locations have immense deposits of it, either naturally or artificially stored. Hikawa created several devices for focused absorption of Magatsuhi, such as the True Core Unit in the Assembly of Nihilo's Shiodome base, the Obelisk and the Nightmare System.
- In Persona 4, Magatsu-Izanagi is the palette swap of the original Izanagi (with different animations). The Magatsu counterpart is tinted red, same as the color of Magatsuhi in Shin Megami Tensei III: Nocturne.