Human Dess (Deltarune Theory)
So while I'm not the first to bring this theory up, this post will be examining the theory that Dess is, in fact, a human. For the first notable evidence, in the Xbox version of Undertale, sans mentions "The antlered girl and her big sister". The way this is phrased implies there's something special about either Noelle or Dess in this instance. Though admittedly this is shakey due to the whole "kill all humans" thing the monsters have in undertale, so either A) Dess pulled a literal jesus and revived herself post-true pacifist (as asgore alludes to her being alive in the undertale alarm clock, EDIT: but the only other mention of her is from sans who mentions her in the context of a blizzard from an unknown point in the past), B) Rudy used his "best friends with asgore" card to get the monsters off his daughter's back (presumably via faking her death) while his family lived in seclusion or C) she's a monster in that universe instead, which makes this piece of evidence fall kinda flat.
The next bit of evidence is that she has a lot of shoes, plantigrade-shaped shoes to be specific. While she does have a pair of shoes fit for a hooved monster (edit: unseen by the way), and the aforementioned shoes could just be an oversight, the fact those hooved shoes are found in a box alongside a bunch of other stuff that aren't hers (like Asriel's retainer), EDIT: not to mention the ice skates she has in her closet and the pair of roller blades which there is check dialouge for but never specifies whether they fit hooves or not (its also strange in general that the unseen pair of shoes is specified as being fit for hooves yet the clearly plantigrade roller blades aren't).
In speaking of her closet, Carol seems to be obsessed with hearts, having a bunch of them in Dess's Closet in particular. Considering how she goes as far as to preserve her daughter's paper snowflakes by bronzing them as ninja stars, this could tie to Dess's human SOUL. EDIT: It's also strange in general why they are there in the first place, considering its doubtful carol put them in post-dessappearance and there's no inplication that dess has an obsession with humans (i feel like that would be brought by now, though i don't doubt the possibility), so I definitely feel like toby wants us to notice this environmental detail.
However, there's this one odd detail that could tie this up in a bow. In the Dreemur household, there are both monster and human-shaped cookie cutters. In the Holiday Mansion, though, there are only the monster-shaped ones, so far so logical. Its phrased kinda weird to me "In the cupboard are... cutters for gingerbread monsters", but fine enough. However, when getting the gingerbread guard from chapter 3 and going into chapter 4 its specifically states that something is missing (implied to be the gingerbread men cookie cutters, which are currently equiped as the gungerbread guard). Its sorta strange to me how it brings up this fact in a strangely coy manner: "The cupboard. It seems to be missing... things". This feels like its going to have some kinda of implication regarding Dess.
Potential Chara Parallels
I'll be missed to not bringing up an interesting observation if this theory (and that dess is the knight) is true, there could be interesting Chara parallels we could draw from this (hell they might even straight up be Deltarune's version of chara, similar to Kris being Deltarune Frisk). For one, we see one of Asriel's Sweaters in her closet, and in Undertale, Asriel shares a similar shirt to Chara there.
9 is stated to be Chara's favourite number, and when the knight SWOONS you it knocks you down to -999 HP. We also know Chara has a thing with knives, and the knight's weapon (which we know the name of via the Black Shard) is the Black Knife, and Chara is often associated with knives (including the genocide-exclusive REAL Knife).
There's also the matter of Asriel's connection to Seam, what with a drawing of him appearing on his desktop, and it's implied that Dess is into making plushes (as per the frayed yard and buttons in one of the boxes in her room and her helping dess make the angel plush). It could also be possible that Dess might be the original "girl with hope crossed her heart", meaning there's a non-zero percent chance that Asriel and Dess might've been involved in the dark world before. Potentially leading to a reverse scenario where Asriel's actions inadvertently led to Dess becoming the Knight, where in Undertale it's Chara's actions that idirectly led to Asriel to becoming flowey.
How this could tie to Dess being the Knight
While this does lead to interesting revelations in regards to Dess and her relationship to Kris, potentially acting as his anchor before she disappeared and why Kris would be so willing to (potentially) backstab their friends, there is one thought i have in regards to Dess being a human and thats found in the Asriel boss fight in Undertale.
You see, when you are knocked down to 0 hit points during the fight instead of dying like normal the soul repairs itself after splitting in half, with it stating "but it refused" the first time this happens. The fight itself last for only a couple of minutes, but what if this ability is stretch to its absolute limits and a human tries to pull an Undyne the Undying as long as feasably possible.
I propose the Roaring Knight is the result of Dess trying to use pure determination to keep herself alive far longer than she should be able to, likely from some unknown injury that led to her going missing for years before resurfacing. This is just an idea unrelated to the wider "Dess is a human" theory, but I do feel like it's something I should point out as a possibility.
EDIT: The roaring knight is more likely Dess's soul in the lightworld, as I theorised here.
