Just learned this song by ear and it only took about 5-10 minutes. Its in Drop D tuning.
Riff 1 (song starts with a pick slide after drums)
d:|-----------------------------------------------------------|
A:|----------------------5------------------------------------|
F:|------------------------8-7-6------------------------------|
C:|-------9---9-9----------------7----------------------------| 4X
G:|-------7---7-7---------------------------------------------|
D:|-----------------------------------------------------------|
[ Tab from: http://www.guitaretab.com/v/venom/334048.html ]
Riff 2
d:|-----------------------------------------------------------|
A:|-----------------------------------------------------------|
F:|-----------------------------------------------------------|
C:|----------3--4---------------------------------------------| 2X
G:|-4--3-----1--2----4-----3-3-3-3-3-3------------------------|
D:|-2--1-------------2-----1-1-1-1-1-1------------------------|
Riff 3
d:|-------------------------------------------|--------------|
A:|-------------------------------------------|--------------|
F:|-------------------------------------------|--------------|
C:|-------------------------------------------|--------------|
G:|-------5h7-----4h5----------5h7------4-3---|-----2--------|
D:|--0-0--------0------0-0-0---------0--2-1---|-----0--------|