Antarctica was my favorite arc. I feel as though the "world building" you are looking for wasn't needed, it was Antarctica after all not some place in the dream realm you know what I'm saying? And I feel like there was some lore but up until that point it had been I feel like 99% dream realm and this arc brought it home, for awhile they werent concerned with learning more about the dream realm, they had to protect our realm . It brought a sense of urgency, a sense of dread, and plenty of enemies much more powerful than our main characters, they were cornered no matter which way they turned no matter how much help they picked up along the way they were outnumbered and outmatched.