Achelous
Achelous, in Greek mythology, a river god. He was the son of Oceanus and Tethys, and father of the Sirens. Achelous had the power of assuming various forms. He unsuccessfully fought Hercules for the love of Deianira. First he changed himself into a snake; Hercules nearly strangled him. Next he became a bull, but Hercules threw him to the ground and tore off one of his horns. According to one story, naiads (water nymphs) consecrated the horn and gave it to Amalthea as the cornucopia (horn of plenty).
Ashamed after his defeat by Hercules, Achelous threw himself into the nearby river, which thereafter bore his name. The Achelous (modern Greek: Akhelóös) is one of Greece's chief rivers, flowing 130 miles (210 km) from the central Pindus Mountains southward into the Ionian Sea. Worship of Achelous was widespread throughout Greece, and extended to Sicily. His name frequently was invoked in taking oaths.