If Darius is played, then Cleave is played to make him ready, but the opponent plays Defy on Cleave, does Darius get ready?

Ruling: No, Darius does not get ready. Cards that are countered by Defy are considered never played, so Darius's ability does not trigger.

Nuances:

• Cards are not considered played until they resolve, so Darius doesn't become ready with +2 until the second card actually resolves