After Theseus helps defeat the boar in Calydon, he heads home to Athens. On the way, he is stopped by a flood caused by the river god Achelous. Achelous invites Theseus into his house to wait out the dangerous flood. Theseus accepts the invitation, and he and his companions enter Achelous’s mossy house. Achelous, who is proud to be hosting a hero, has nymphs serve Theseus and his friends a banquet.
Although Achelous is a river god, he is honored to be hosting Theseus—a human war hero. Achelous shows Theseus veneration by inviting him into his house rather than the other way around. This shows that the gods are often intrigued and impressed by humanity and what it is capable of, even without omniscient power.
While he dines, Theseus asks Achelous about the islands that he sees scattered throughout the water. Achelous explains that these islands used to be naiads who had neglected to honor Achelous in a festival. Angry at being forgotten, Achelous had swept a flood across the land that drowned the naiads. Achelous then split the land into five islands. Achelous then points to a small island that had once been Perimele, a girl Achelous had loved and raped. Perimele’s father had pushed her off a cliff when he found out she was no longer a virgin, but Achelous had sought Neptune’s help in turning her into an island.
Achelous’s story is an example of creatures being transformed into landforms. In this case, the naiads were transformed as punishment for refusing to worship Achelous. However, one of them was transformed into an island to save her from death. In this way, the same transformation—in this case into islands—can be to either punish or save. This suggests that transformation itself can be both a blessing and a curse.