In Demonology he/she is a Prince of Hell.
Usually spelled Ashtaroth or Asteroth
With the rise of Christianity many of the old gods were labeled as demons.
Well, Asteroth is not a “he” but a female “goddess” common in most pagan mythologies under a variety of names. Don’t know about demonology, but Asteroth is the equivalent of Astarte, Ishtar, Semiramis, Isis, and Eostre also known in pagan religions as the “Queen of Heaven”, and is celebrated in the pagan fertility festivals which probably were the basis of much of the traditions of “Easter” in the western world.