The riff is in Drop C#, but you can play it in Drop D if you like, it'll just sound a little higher. There are really only two chord shapes for the main riff, one is 0 9 x 11 x x (open low e, 9th fret on A string, muted d string, 11th fret on g string, muted b and e, then the second one is either 9 9 11 0 x or 9 9 11 x x x, they both sound right to me and i tend to switch between. on the second chord you occasionally fret the 10th fret on the low E string, and occasionally you move the first chord shape around the fretboard.
the second riff at the more end part of the actual song on the record is just power chords and harmonics. it's just the open powerchord and harmonics on the 4th and 3rd fret. you can't really play this riff on acoustic since those harmonics on the 4th and 3rd fret need Really high gain to be audible
