Belphegor

Representing the demon Belphegor and the corresponding the sin of Sloth. Belphegor's appearance is a girl with long dark hair in a pony tail. She is hard working and sensible, to make her target fall all the harder. She is the middle child of the "Stakes of Purgatory."

[Spoiler] She is the fantasy version of one of the servants that used to bully Sayo Yasuda as a child. [/Spoiler]

(Source: Wikipedia)