Laymia

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She is Lamia's mother and appears to be one of Behemoth's most trusted advisors, as well as the leader of the 34 Pillar Division prior to Jabberwock's return.
Despite her daughter aligning with Beel, she is a key architect of the scheme to assassinate Oga Tatsumi and strip the demon infant of his Contractor, thereby enabling En to ascend the throne.