Achelous was a Greek demi-god, son of Oceanus & Tethys. He was just one of their 3,000 river god sons, all vital men with horns jutting out of their foreheads & having long beards. He was depicted as having the lower body of a snake & the upper body of a man. Achelous's domain was the largest
watercourse in Greece.
He had the misfortune to fall in love with a mortal woman named Deianeira, but unfortunately, so did the hero Hercules, so the fight was on! Achelous fought valiently, magically shapeshifting into a snake & a bull, but weh Hercules tore off one of his horns, that ended the battle. The river nymphs found the horn & transformed it into the Horn of Plenty.
Don't feel too sorry for Achelous, for he was a hard god to please & very picky about the sacrifices offered to him. The daughters of the soothsayer Echinus found that out the hard way when Achelous turned them into the Echinades Islands, after they presented him with a disappointing sacrifice.