It's sounds like a pretty medium distortion setting (More of a hardrock/rock and roll crunch as opposed to full-out distortion, similar to what 80's bands would call heavy) and it is the riff being harmonized up a perfect 4th interval, if I'm not mistaken. You can get this effect by using more than one guitar player, and having one player playing the riff and then the second playing the same riff but up a 4th. Or, you can just use a harmonizer pedal of some kind.
Hope this helps. Badass song, I love Rage.