A few details are starting to leak out … the incipit of a piece from Reuters:
Mads Mikkelsen, Gemma Arterton and Alexa Davalos are joining the cast of “Clash of the Titans,” the Greek-god epic being directed by Louis Leterrier.
Sam Worthington stars as Perseus, who embarks on a quest to save a princess and defeat Hades, the god of hell. Matt Manfredi and Phil Hay wrote the script.
Mikkelsen is playing Draco, a skilled fighter and leader of the Praetorian Guard that accompanies Perseus.
Screenrant adds:
Arterton’s character will be “lo” a demi-goddess who Perseus falls for (although I’m guessing the romance doesn’t work out). The character is a new addition to the story and did not appear in the original film – which is a good sign (IMHO) that the filmmakers are really trying to re-imagine the entire concept of Clash of The Titans, rather than trying to re-hash the original. We’ll see how it turns out.
Personally, I think they should get rid of the Kraken … there are enough monsters in Greek mythology they could use …
rogueclassicism 
Rescuing a princess from Hades? Isn’t that the plot of the Disney Hercules from a few years ago? And, really, can’t they come up with something a bit more creative and non-anachronistically Judeo-Christian than “Hades = Satan with a chiton”?
FTFA: “Mikkelsen is playing Draco, a skilled fighter and leader of the Praetorian Guard that accompanies Perseus.”
*Insert facepalm here*
For those less conversant with Greco-Roman history, let it be known that “Praetorian Guard” is Roman, not Greek and a good many centuries removed from the Perseus legend/myth.
And people wonder why am so cranky when it comes to history.