Achelous

In Greek mythology, the son of Oceanus or Sol, by Terra or Tethys, god of the river of the same name in Epirus.  As one of the numerous suitors of Dejanira, daughter of Ceneus, he entered the lists against Hercules, and being inferior, changed himself into a serpent, and afterwards into and ox.  Hercules broke off one of his horns, and Achelous being defeated, retired in disgrace into his bed of waters.  The broken horn was taken up by the nymphs, and filled with fruits and flowers; and after it had for some time adorned the hand of the conqueror, it was presented to the goddess of Plenty. Some say that he was changed into a river after the victory of Hercules.  This river is in Epirus, and rises in mount Pindus, and after dividing Acarnania from Aetolia, falls into the Ionian Sea.