Is it obvious that Kris is my favorite character?

*ᴛʜᴇ ꜱᴏᴜɴᴅ ᴏꜰ ʀᴜꜱʜɪɴɢ ᴡᴀᴛᴇʀ ꜰɪʟʟꜱ ʏᴏᴜ ᴡɪᴛʜ ᴅᴇᴛᴇʀᴍɪɴᴀᴛɪᴏɴ

I mean, the Dark Sanctuary doesn’t really have the water theming but… they are both the darkest parts of the game, both in a literal visual sense. With a mostly darker color-scheme and puzzles themed around darkness

and also in the narrative sense, being the most serious, solemn and grim part of the game. While Waterfall has its moments of levity and, y’know, Temmie Village, there’s a lot more focus of scenes of melancholy or fear compared to other parts of the game. While Undyne can be a very silly character, she only shows that side of herself to the Human during her Boss Fight right at the end and she’s otherwise a quiet and no-nonsense antagonist.

Deltarune Chapter 4 is the darkest chapter of Deltarune so far. It also has it's funnier moments but… The Church Dark World concept leads itself to much more serious theming and designs for the backgrounds and the enemies, it has some of the most serious exploration of our main characters' personalities and arcs, and has a lot of emphasize on the fact the stakes have been raised and Shit Just Got Real.

Plus, both Chapters deal heavily in the lore written on the walls of that area

Including a Prophecy

(well, in Deltarune it's exclusively a Prophecy, in Undertale it focuses on History and also includes a Prophecy)

And on a larger scale, both of these writings introduce the idea that the information we/the characters had before on the Lore is not the full picture.

And y'know, Gerson, who is present in both areas but also…

As the Hammer of Justice he also serves as a very heavy parallel to the Boss Fight(s) against Undyne in Undertale, both in visual design and gameplay (the Green Soul Mode).

Also, y'know, Piano Puzzles...

The thing is just… I didn't quite know what to do with this comparison. I mean, speculating on the idea the next Chapter would somehow be a Hotland Counterpart feels incredibly silly considering we already had two Dark Worlds that are very Hotland-like…

Which is when I realized, what if Deltarune Chapters correspond to Undertale areas but in reverse?

The Dark Sanctuary is like Waterfall and before it, TV World is a lot like Hotland, focused on TV-themed minigames controlled by an attention-hungry rectangular Game Show Host.

Cyber World would be the CORE, as the most high-tech themed areas in their respective games

And Queen and Spamton both including elements of Mettaton EX/NEO

Including Spamton NEO having the Yellow Soul Mode.

And Card Castle is the counterpart to New Home. Since these areas are both meant to be, well, a castle and it's surrounding area.

And King obviously being kind of a dark thematic reflection of Asgore.

…That would make Chapter 5 a Snowdin parallel to some degree, then Chapter 6 as a Ruins parallel, leaving Chapter 7 to do something totally off-the-rails and unique and unpredictable… Question is just what would that mean for Chapter 5 to be a "Snowdin Parallel"?

Since the Dark Sanctuary didn't really have water and TV World didn't really have magma-stuff, I don't think that would mean Chapter 5 would necessarily be an ice world, and indeed the only real hint we have to Chapter 5 right now is about a garden.