Cosmo

Cosmo is the Cosmos Fiend, and was one of Quanxi's harem members.

Supernatural Abilities
Total Understanding: Cosmo can force her target to understand everything in the universe. This renders them in a semi-catonic state in which they are "only able to think of Halloween until they die". Once this occurs, the victim will be unable to think or say anything other than the phrase "Halloween" until their death.

Trivia

 * While this fiend is named as Cosmo in the manga, it is named as Zombie (ゾンビ, Zonbi) in the Character Popularity Poll.