According to Herodotus, Onomacritos induced Xerxes, the King of Persia, by his alleged oracular responses, to decide upon his war with Greece.
And Pausanias, in explaining the presence of the Titan Anytos at Lycosura, said that "Onomacritos took the name of the Titans from Homer and composed orgies for Dionysus and made the Titans the actual agents in the sufferings of Dionysos." Therefore, Onomacritos is responsible for inventing an important aspect of the mythology concerning the Titans.
Sources:
Harpers Dictionary of Classical Antiquities, by Harry Thurston Peck. New York. Harper and Brothers, 1898.
Prolegomena to the Study of Greek Religion, by Jane Ellen Harrison, Cambridge, 1903.