Interesting part from the trailer:
-"Prophecies speak of Arthur's bane. You would do well to fear it for it stalks(not sure for this) like a ghost"
-"Prophecies do not lie. Arthur's bane was real. Once it was known to us, his end was nigh."
I think...but does anyone know what this whole "Arthur bane" thing is about ?
This is just a guess but based on the definition of the word, I think Mordred is Arthur's bane.