The demo is called 'Velocity Attack' and is a prequel sequence with a boss showdown. A different demo will be on hand at this year's TGS.
Shinji Mikami revealed a 'surprising character' would be a part of the special Tokyo Game Show demo for Vanquish. The game is apparently done with Vanquish releasing on Xbox 360 and PS3 October 21st. Are you excited for Sega's 'Gears of War on crack'?