Agrat bat Mahlat (אגרת בת מחלת) is a demon in Jewish mythology.
Mahlat and Agrat are proper names, "bat" meaning "daughter of" (in Hebrew).
In the rabbinic literature of Yalquṭ Ḥadash, on Tuesday and Friday nights, she is "the dancing roof-demon" who haunts the air with her chariot and her train of 18,000 messengers of destruction.
Agrat then mated with him a night and bore him a demonic son, Asmodeus, who is identified with Hadad the Edomite.
Mother and daughter were exiled to the desert, where the demon Igrathiel mated with Mahalat and engendered Agrat or Igrat.