The Monster is an evil spirit that appeared in the Devilgram Say His Name, where it devoured Beelzebub and MC and would only release them after Beelzebub guessed its name. As of now, this character has not appeared in any other Devilgrams or in the main storyline.
Little is known about it, but it is very hostile toward humans and especially volatile towards Beelzebub for forgetting it. It also knows the brothers, Diavolo, Barbatos, and Solomon, and holds negative views towards them.
It also revealed that it loves sleeping and its younger sister.
- The monster was a manifestation of Belphegor, which could be similar to the entity Mare.