If you look to the Right hand bottom corner of these pics you can see  Riddick...

These are taken at the beginning of the Trailer when Aareeon is coming out with the Necromongers.  After watching the trailer many many many many many times... *laughs*  I figure that is Riddick being led into that chamber by Thandie Newton's Character.. When she says "The more you resist them the greater the damage will be..."  My best guess anyways... *grinz*