Revealed by Big Finish on 10th August, the full cast list and the real cover for this month's audio release, Black And White. Here's what they have to say:
The TARDIS arrives in the land of the Danes, where a young warrior seeks to rid the kingdom of Hrothgar from a cruel and terrifying demon. The brave young warrior is Beowulf; the monster is Grendel... or so his name will one day be written. But what's written down in black and white is sometimes very far from the truth – as the Doctor knows, and his companions are about to discover.
...original details posted below.