Yoru is the war devil who currently occupies the body of a human and is now considered a fiend. She is one of the four horsemen in the series and is also the main antagonist of the academy saga.
The actual form of the war devil is similar to that of a dark-colored owl. Pochita may have consumed the majority of Yoru's body after losing against him in the past, leading to the development of this depleted form.
The war devil took over the body of Asa Mitaka and has taken on her appearance as well. However, she added scars across the center of her face and her left cheek. In addition to this, she has multiple rings around her eyes. Yoru consistently dons the same attire as Asa, typically a school uniform.
Personality-wise, the war devil is extremely confident and prideful. She is also similar to Makima in the sense of using people to achieve her own goals without remorse. However, unlike her fellow horseman Makima, who only saw a chance to triumph against Chainsaw Man, Yoru is self-assured and proud, pledging to reclaim the Nuclear Weapons from him.
Yoru has all of the typical devil abilities, including the capacity to make contracts with people in exchange for money, the capacity to heal herself by ingesting blood, the capacity to take control of a dead person's body and consciousness, the capacity to transform into a fiend, and the capacity to come back to life in Hell after death.
Yoru can transform everything in her possession into a weapon. Both inanimate and living things are covered by this. Yoru must touch what is hers and cry out the name of the weapon to start the weapon change. The remorse Yoru and/or Asa feel for developing the weapon is inversely correlated with the weapon's power.
Despite being a member of the Four Horsemen, the War Devil asserts that after Chainsaw Man half consumed her body, her Devil's power diminished. Her original power has been significantly decreased as a result of this as well as the prolonged absence of conflicts in the human world