Pandemonium is a major antagonist, with the Pure Concept of Chaos.

The daughter of Countess Libelle and older sister of Manon Libelle, Pandemonium is a Lost One that became one of the Four Major Human Errors with her Pure Concept of Chaos.

Described by her mother as a bright girl "full of energy" who adores singing and dancing, Pandemonium is cheery and playful, though with her Pure Concept and becoming a Human Error, she has no memories or identity associated with her previous self. Rather, her sole purpose has transformed into inflicting as much chaos as possible.
Her mother also commented that Pandemonium loves movies above all - after becoming a Human Error, Pandemonium states that she loves horror movies and strives to replicate them, likely due to her Pure Concept.



(Source: The Executioner and Her Way of Life Wiki)