Death Devil

The Death Devil (の) is the Devil that embodies the fear of death and a member of the Four Horsemen. She was mentioned by Makima, who sought to eradicate the other Horsemen, and later mentioned again by Hirofumi Yoshida.

Her existance was properly explained by Nayuta, as "The Great King of Terror" the eldest of the Four Horsemen and the strongest Devil.

Appearance
The Death Devil's appearance is currently unknown.

Personality
The Death Devil's personality is currently unknown.

History
The Four Horsemen and the Weapon Devils once engaged in a brutal battle against Pochita in Hell. However, in the midst of the battle, Pochita mysteriously vanished. Despite searches by the Control Devil, Pochita could not be found. Unbeknownst to the Four Horsemen and their underlings, this was because Pochita had changed forms on the verge of death and escaped to Earth.

Dating Denji arc
Hirofumi Yoshida knew of the Death Devil's existence, and how by swallowing Devils Pochita could erase their presence from the world. While trapped in the aquarium, he wondered to Denji if Chainsaw Man would be willing to eat the Death Devil for humanity.

Current arc
When talking about The Prophecy, Barem Bridge mentions that "The Great King of Terror" will descend in 6 months time. Nayuta who has innate knowledge of both the prophecy and Four Horsemen, revealed that "The Great King of Terror" is in fact the Death Devil herself. Nayuta elaborates that Death is their eldest sister and the strongest devil.

Abilities
As a Devil, the Death Devil possesses all of the standard Devil abilities. She is the strongest Devil.

Trivia

 * Given Death’s nature as a fear, it's possible that the Death Devil is also counted as a Primal Fear.