Behistun Inscription
The Behistun Inscription, which offers greatest insight into the events during this period, mentions a rebellion in Egypt which occurred at the same time as other rebellions in the eastern parts of the Persian Empire. Darius I, the author of the Behistun Inscription, does not go into any detail about how he dealt with the rebellion in Egypt. Polyaenus reports that Darius moved to Egypt to suppress the revolt, and entered into Memphis during the mourning for the death of an Apis bull. Cunningly, the Great King promised a hundred talents of gold for the one that would provide a new Apis, impressing the natives to the point that they moved en masse to his side. This story suggests that the rebellion wasn't yet quelled before Darius came to Egypt in 518 BC.