|“||Those who are swallowed by madness...swallow madness...melt into madness...and harden with madness.||”|
Crona unleashes an great tidal wave of Black Blood that engulfs and encapsulates any opposition within the darkened depths of this gigantic swell, permanently. To represent the terror epitomized by this technique and the resultant drenching insanity, numerous shadowy figures appear in the wave of Black Blood, some with beady eyes, some with no eyes and just ravenous drooling mouths. Crona also assumes a deformed appearance, with the bottom half of their body swelling up to a bud-shaped shadow emblazoned with the three eyes of Asura.
Once consumed by the torrent of Black Blood, the opponent is assaulted by these shadows made from Black Blood, which enters their bodies and causes their entire physical body structure to melt into Black Blood. Once they have melted, the Black Blood hardens into a large sphere. This sphere, known now as Black Spheres by others (黒球 Kokkyuu) also emanates a strong Insanity Wavelength, making it harmful for anyone near it or in physical contact with it.
This hardened sphere of Black Blood that is all but impossible to escape from, with it even proving resistant to the Demon-Repelling Wavelength (退魔の波長, Taima no Hachō) emitted by Tsar Pushka and other techniques that should present an ideal counter to Crona's Black Blood. Even Maka's powerful Anti-Demon Wavelength does not work. Although the amount of insanity contained within this sphere is immense, Maka has seen that the casualty's soul is still active inside the sphere, meaning that there may still be a chance of survival.
Mad Blood, however, can grow powerful enough to engulf an entire city, flooding it like a tidal wave, melting all of its people and buildings and hardening into a gigantic black sphere.
Mad Blood is first used in the fight against Feodor and Tsar Pushka, which Crona manage to defeat with this move. Later, Crona uses it to engulf a town in Ukraine. Maka and Soul have currently tried to break the Black Spheres Feodor and Pushka are in with Majin Hunt, but the only result is that Soul ends up going temporarily insane with the Black Blood.
Mad Blood was also used during the final fight in the moon against Asura, from inside him, using the powers of the brew to greatly enhance it, Crona unleashed a final Mad Blood with all their power, combining with Asura's own Black Blood to dissolve both of them in a gigantic sphere of Black Blood, enough to completly engulf the moon and a slight amount of insanity from Crona's emotions being felt from the earth.
It is currently unknown as to whether this ability is simply derived from the Black Blood in question or instead, an actual evolution of it.