They imagined him as having the Earth at his feet and in his hands the stars and a scepter, demonstrating his superiority. In other allegories, it is a wheel, attached by a chain, under a rock and with two cornucopias - illustrating its inflexibility and luck.
Representing fatality itself, "Destiny" dictates events, and even Zeus cannot help it. Its laws are written in a book, the access to which is possible, and yet in an obscure way, by the oracles.
He could also be called Aeon (eternal time), and they consider him the husband of Ananque and father of the moiras (parches in Rome). To represent him, the Greeks had Moiras, whom they consulted with the gods - to no avail, since destiny is immutable.