Hail!
A blackish thrash approach is just what this theme needs! Very Haunted/The Crown-esque.
Only complaints: The snare is a little too round-sounding, and I think the tone change for the mellow part takes you out of the song a bit too much. Maybe you should have left the distortion the same, but flipped pickup switch back to the neck for that.
The riffing is robust throughout and a pleasure to listen to. Good work, man.