TV-Series
Description
The Nibelcole are a collective group of artificial beings referred to as Pseudo-Spirits that appear in the fifth season of the series. They were created by Isaac Westcott through a combination of DEM's Realizer technology and the power of his Demon King, Beelzebub. Their primary purpose was to serve as personal assassins targeting Shido Itsuka, as Westcott believed Shido had already established enough connections with the Spirits and needed to be eliminated. Westcott intended that killing Shido in front of the Spirits would cause them to invert from sheer despair. Later, the Nibelcole were reorganized to become the vanguard of DEM's forces during the final battle against Ratatoskr.

In terms of personality, the Nibelcole are fanatically devoted to Westcott, regarding him as a father figure and obeying every order without question. They are easily angered by any insults directed at their creator. As a collective, they display a single-minded focus on their mission and little in the way of individual identity. A profile remark about them notes that their appearance resembles a bean sprout, but their brain is like that of a gorilla, suggesting a deceptive combination of unassuming looks and aggressive, simplistic thinking.

Their motivation is entirely centered on serving Westcott's will, first as assassins and later as frontline soldiers in his war against Ratatoskr. They show no hesitation or fear in combat and are generated in large numbers from the pages of Beelzebub, making them a virtually inexhaustible force.

In the story, the Nibelcole function as a major antagonistic force during the conflict between DEM and Ratatoskr. They are initially deployed to assist Ellen Mathers in assassinating Shido. During the all-out battle above Tengu City, they engage Kurumi Tokisaki's clone army and target Ratatoskr's ground artillery. Their numbers and near-immortality make them a persistent threat that the Spirits and Ratatoskr must overcome. At one point, Shido uses the Angel Haniel to transform himself into a Nibelcole in order to hide among their ranks and launch a surprise attack on Westcott.

Regarding key relationships, the Nibelcole share a strong bond of devotion toward Westcott, their creator. They have no meaningful connections with other characters and are purely adversarial toward Shido, the Spirits, and Ratatoskr.

Development is limited for the Nibelcole as individuals, as they function as a uniform force. Their role shifts from assassination units to a full-scale army, but their core behavior and function remain unchanged.

In terms of notable abilities, the Nibelcole are classified as Pseudo-Spirits wielding the Demon King Beelzebub Yeled. They use book pages as weapons and wear an Astral Dress called Chaigidel-Yeled, which resembles a miniskirt-length nun's habit. They can be generated endlessly from Beelzebub's pages, giving them a virtually immortal presence on the battlefield. Their physical parameters include a height of 158 centimeters, with very high agility as their standout attribute, supported by moderate strength and spiritual power. The collective and renewable nature of the Nibelcole is their most defining tactical asset.
Cast