I like how dungeons and transition areas look like, the reef + cthulhu sculptures are nicely blended into underrail cyberpunk + cave theme.
The music sounded great, perfect balance between ambience and noticable melody/tunes. Better than most background music I heard because it was usually too ambient/bland for my taste. This also make it unsettling which fits exploring those dungeons perfectly, but can be tiresome, so I will probably turn the music down/up depending on my current mood.
Overall, I just can't wait for the expansion.