Theseus and Achelous
According to Ovid, Theseus stopped at the banks of the stream Achelous on his way home after hunting the Calydonian boar. There the river-god entertained him with feasting and storytelling. A son of Oceanus and Tethys, Achelous was said to be the oldest of the three thousand river-gods.
       Classical Source. Ovid, Metamorphoses 8.546—610, 9.1— 134