It's from the producers of 300, it has nothing to do with the battle of Thermopylae. Looks like it actually is about some sort of war between the titan army of Hyperion and an army led by Theseus, which is kind of funny since nothing even remotely close to the plot of the movie is ever mentioned in mythology.
I might see it for the fight scenes if it looks good enough, although it does kind of bother me that they're taking random characters from mythology and having them fight, especially considering the characters were never said to have even interacted. I'm a bit of a mythology nerd though, so most people probably won't mind.