That video is a preview to a nearly 40 minute discussion on Death Metal Guitar Theory on Patreon, which only costs one dollar to unlock (plus, you get access to OVER 100 other video lessons!)
Below are tabs of scales I like to use when composing death metal.
The reverse gallop rhythm is quite common in death metal guitar playing. This etude can help you work on your reverse gallop picking chops.
In the video demonstration the tuning is in B standard. You are welcome to play this in any tuning you want!
Here are the tabs:
Here is the drum track used (you can download this and change the tempo to suit your current skill level)
Available Instruction Courses