Asterion is a river-god, presumably one of the sons of Oceanus and Tethys. Asterion was one of the three river-gods (the other two being Inachus and Cephisus) who awarded the territory of Argolis to Hera over Poseidon. Poseidon, in anger, made the waters of all three rivers disappear so that they don't flow unless it rains, and are dry in summer.