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Who are Oceanus and Tethys' children?
River-gods (sons) and Oceanids (daughters)
Notably:
Achelous, the god of the Achelous River, the largest river in Greece, who was defeated by Heracles in a wrestling contest for the right to marry Deianira
Alpheus, who fell in love with the nymph Arethusa, pursuing her to Syracuse, where she was transformed into a spring by Artemis
Scamander, who fought on the side of the Trojans during the Trojan War, and, offended when Achilles polluted his waters with the a large number of Trojan corpses, overflowed his banks nearly drowning Achilles
Metis, Zeus' first wife,
Eurynome, Zeus' third wife, and mother of the Charites;
Thetis who nurses Hephaestus back to health