ive tabbed quite a few of their solos.
for solos they use either harmonic minor or pure minor for their solos, or a combination of the 2.
most of their riffs are diminished, augmented (not sure if its called augmented, il explain below), harmonicminor and chromatic.
diminished (or whole half scale)
1 2 4 5 7 8 10 11 etc (this are the notes on 1 string).
augmented (i think)
1 2 3 5 6 7 9 10 11 most of their harmonies on conque the throne and king of all kings are based on the augmented thing.
e-------------------------------
b------------------------etc----
g-------------------3-4-5-------
d-------------4-5-6-------------
a-------5-6-7-------------------
e-6-7-8-------------------------
not sure it this makes alot of sence, im not verry good at explaining.
u can pm me if u want to know some more or better explanation or anything