Who Goes There modulations - 2 parts in 1

Tuning: drop C + low G
There's 2 modulations happening here.

The first one (half step up) may be recorded in drop Db tuning (surely more comfy to play); the options may vary because with 2 guitars and a bass you can still use one tuning since every instrument plays a different part.
When it comes to figuring out a song tuning, I rely on hearing if there's any open string ringing out.

Also, the song accelerates after a few verses, it makes me think they probably recorded it live.
It continues with that section in G#, then it's only Billy singing over a variation on Db Ab Ab/F (or Fm).
Then they repeat the section in C (the second modulation) and cut the last F chord shorter than before, leaving the bass closing with the last 3 notes:

C A E
G-5----/14----\9----|
C-------------------------|