Since director Zack Snyder is busy overseeing the rebooting of the Superman franchise, Man of Steel, he has passed the helmer duties on the in-development 300: Battle of Artemisia (which has apparently not been re-dubbed Battle of Artemisium, previous reports to the contrary) over to Noam Murro, an Israeli filmmaker whose sole feature-length directing effort to date is the 2009 indie dramedy Smart People.
Murro has so far proven competent, when it comes to casting the new Frank Miller comic book adaptation, having approached Joel Edgerton (Warrior) to headline the film as the famous Greek general, Themistocles. While the well-regarded actor passed on the opportunity to appear in Battle of Artemisia, the search is seemingly on for a leading man of equal caliber.
Heat Vision is reporting that Eva Green has begun talks to play the film's female lead role: namely, the eponymous Artemisia, who encourages the power-mad Persian leader Xerxes (played by Rodrigo Santoro in 300) to declare war against the Greeks and also attempts to win Themistocles over, via her "vindictive charm." The character is seemingly based on the real-life historical figure Artemisia I of Carla, who did in fact counsel King Xerxes and served as his sole female commander.
However, in the 300 spinoff/semi-prequel, Artemisia looks to function primarily as the femme fatale who uses her looks to manipulate the men around her, in order to better serve her own (selfish) purposes - while not actually participating in battle herself. Miller's stories are often accused of having misogynistic overtones and it sounds like Battle of Artemisia (which is based on his Xerxes comic book) will attract similar criticisms, for that reason.
That said - who better to portray a lovely seductress than Casino Royale's Vesper Lynd (ie. Green)? Besides, it's certainly possible that the BAFTA-winning French bombshell's take on Artemisia could feel similar to her version of Morgan on Camelot - who is more of an interesting and complex (not to mention, capable) villainess, rather than a simple "evil woman."
300: Battle of Artemisia is still only in the beginnings of the casting process. We will continue to keep you updated on the status of the project, including any new information about its potential production timeline.