It's a reused track from 1.0 but I absolutely love Hullbreaker Isle's theme, to me that dungeon perfectly encapsulates the feeling of adventury and discovery that's promised to you at the start of the game, and I think like 75% of it is due to the music lol

Antitower is just beautiful, I love the instruments, the melody, everything... it might be my favorite dungeon theme in the whole game.

Lastly shout outs to Swallow's Compass, I'm not a big fan of the flute at the start but it ends up transitioning into one of the most heroic tunes in the game, even if the dungeon and the story around it don't entirely reflect that.