As a result, only one who can withstand Excalibur's numerous flaws can effectively use him.   is the physical embodiment of madness through knowledge. He is the author of the Book of Eibon, which contains blueprints of several other artifacts called that DWMA and Arachnophobia attempt to utilize. The most powerful of these demon tools is "Brew", a small mechanical cube that possesses the power to drastically increase the soul wavelength of anyone who holds it. In the anime adaptation, Eibon allied with Arachne 800 years in the past to cure his lover from a fatal illness, but Eibon failed and resurfaced years later to transform himself into a demon tool used to unlock Brew as penance. The Great Old One that embodies madness through power has the appearance of a black, amorphous blob. His madness wavelength has those it afflicts reveal their true desires as the madness magnifies it. As consequence of its power, this being is responsible for Asura becoming the "kishin" and goes into solitude within the Book of Eibon after Noah collected it. From its prison, the being resolves to use its madness wavelength to test those worthy to take over when the Great Old Ones are all gone. The being puts Black Star and Death the Kid through its test by having them battle each other, deeming their generation ideal successors when they reach a mutual conclusion of what kind of world to create without causing misery through power.   is a black cat with exceptionally strong magic powers, including the power to transform into a young, alluring human woman among other spells, such as conjuring pumpkin-shaped explosions and summoning a giant flying pumpkin for transportation. Her name is derived from "The Blair Witch Project". She is mistaken for a witch by Maka and Soul at the beginning of the story because of her witch-based clothing, such as her pointed hat, forcing them to restart their soul collection after they collect her soul, which she survives since cats have nine souls. She has a flirtatious relationship with Soul and moves in with him and Maka for this reason, much to Soul's dismay and Maka's jealousy. Despite this, the two are able to generally tolerate her presence, though Soul suffers from nosebleeds whenever he sees her doing something risqué. The is a being who appears in Soul's subconscious after he is infected by Ragnarok's black blood, taking the form of a small, red oni in a black double-breasted suit. He periodically tempts Soul through his interests in music with power that can only be obtained through the black blood, hoping to spread its influence to others.