Miller is preparing a follow-up now titled “Xerxes,” which begins about 10 years before the events of “300,” and Snyder has expressed interest in it as a film property as well. “It’s the battle of Marathon through my lens,” Miller said Wednesday. “I’ve finished the plot and I’m getting started on the artwork.”The Battle of Marathon? So we're gonna get dudes in swords and sandals chopping up a bunch of runners? Count. Me. In.