Ishtaar, Astarte, Treasurer of Hell, Diabolos
prophecy, secrets, knowledge of the fallen angels, liberal arts, transforming men and animals, destroying buildings
An angel riding on a dragon, carrying a viper in his right hand. The grimoire consensus is that he has truly terrible breath, so stand some ways away and use a magic charm of some sort to deal with the stench.
Ashtaroth has an unusual level of status and prestige, based largely on his being the medieval incarnation of one of the greatest deities in the history of deity, but that second-hand status seems to be the end of Astarte/Ishtaar’s legacy. In one hierarchy he’s a member of the dark trinity of powers, along with Beelzebub and Lucifer.
If you haven’t read up on her, Ishtaar/Astarte/Inanna was a Mesopotamian goddess of love and war, her history going quite far back to around 4000 BCE. Her myth influenced the myths of Aphrodite, Persephone, and others: she may have even been the consort to El himself under the name Ashera. She seems to have been at least somewhat syncretized with the goddess Isis, and may live in that myth through the current day. She was extremely powerful, as goddesses go: not content with just being the goddess of love and war, she managed to acquire the complete set of divine powers, including “destroying cities,” and stormed the underworld to get those secrets as well (though that didn’t work out for her, in the end.)
No real resemblance to the demon Astaroth, however. In the very early grimoire Book of Abremelin Ashtaroth is listed as a male demon, and that seems to stick. Since Ishtaar/Astarte/Inanna seems to have left her fingerprints on every major western goddess figure (including, possibly, Mary), this unpleasant, stinking shell of a demon may be something the goddess was happy to leave behind, a demonized version of one of her many names.