Dropped D Tuning
They play this on a seven string, but is arranged for a six string.

Begining Riff
|-----------------------------------------------|
|-----------------------------------------------|
|---12-12-12-/-14-\-7-7-7-7-/-9-9-9-9-9-9-9-9---|
|-----------------------------------------------|
|---10-10-10-/-12-\-5-5-5-5-/-7-7-7-7-7-7-7-7---|
|-----------------------------------------------|

Guitar 2
|------------------------|
|---12-\-7-/-8---|---12-\-7-\-5---|
|------------------------|
|------------------------|
|------------------------|
|------------------------|

Main Riff
|----------------------------------|
|----------------------------------|
|----------------------------------|
|---5-5-5-5-\-0-0-0-0-/-2-2-2-2----|
|---5-5-5-5-\-0-0-0-0-/-2-2-2-2----|
|---5-5-5-5-\-0-0-0-0-/-2-2-2-2----|

Every other time substitute a 7th chord instead of a 5th.