According to several sites, Thomas Haden Church, Mark Strong and James Purefoy have now join the cast of John Carter of Mars. Church, who has been rumored to be attached for months, will play the villainous thark Tal Hajus; Purefoy, who stars in Solomon Kane, is Kantos Kan, John Carter's friend from Helium; and Strong, also rumored for months is Matai Shang, the leader of the Therns. But the Therns nor Matai Shang is in A Princess of Mars. Either Stanton is combining elements from both novels, pulling a Lord of the Rings and filming all three at once or somebody has got the wrong information. We'll wait and see.
Well apparently the casting is true. Again all three are good actors but the announcement of Mark Strong as Matai Shang and the description of Kantos Kan as "the captain of the Xavarian, the kingdom of Helium’s grand warship" makes it sound like Stanton is planning ahead for The Gods of Mars. In any case with these characters now cast the film is looking good.