Damn this song is immediately different from the rest of the others. I REALLY dig the sample at 0:00 and how it sounds like it's glitching. It's kinda lofi/chillwave and that's really damn cool. It sounds like an unreleased track from HOME.
One criticism I have is the sleighbells. The rest of the song has this sorta lofi filter over it, but the sleighbells not having that really takes me out of it.
As for the theme of 'crystal castle'. In crystal-y-ness, it certainly hits it. But as a castle? I'm not so sure. That would probably mean the inclusion of orchestral or a large reverb effect to go over instruments to simulate reverberance in an large open space.