Laymia

She is Lamia's mother and seems to be one of Behemoth's closest advisors and the one in charge of the 34 Pillar Division before Jabberwock's return.

Although her daughter sides with Beel, she is one of the main architects in the plot to kill Oga Tatsumi, and deprive the demon baby of his Contractor in order for En to ascend the throne.