More novel and interesting than many other theories, it's entertaining to see.

As for my personal beliefs... I don't presently place stock in it. Core influences towards my own Knight theories are:

• "Black Knife" sounds suspiciously similar to "Burn in Despair!" from Undertale. As do some attacks from the Knight resemble God of Hyperdeath's attacks. "Burning Eyes" honorable mention as food for thought, with "ERAM"'s name being "MARE" backwards, and "Your Best Nightmare" being another Asriel track.

-we know "dark worlds" created by different individuals produce different outcomes seemingly based on the perception/psychology of the person creating them, as Susie's fucked up iteration of the Sanctuary exposes. However, all other Dark worlds-- whether created by Kris, the Knight, or someone else-- are all identical and compatible. It is my personal belief that Asriel and Kris share the experience of making Dark Worlds, and that their cohesive, compatible, carefully crafted visions produce virtually indistinguishable Dark Worlds; their united childhood, their video game programming, their passions, their memories... essentially such harmonious minds, there is no disharmony in their Dark Worlds. The Promise In Our Hearts....
we know Kris made Some Dark Worlds, but yet there are others that were made while they were occupied (at Noelle's house). So someone else (on the phone...) takes care of it. I believe that is Asriel. SOMEONE also physically kidnaps Undyne into the Shelter. This is stupid I admit, not all my thoughts are clever. But it's interesting how fuckin fast that shadow is and that Asriel has medals in Cross Country lol. Uhm maybe he's fast.

-I believe if Noelle made a Dark World, it would differ significantly, like Susie's had. It would be colored by her private and unique feelings.

-When Tenna discusses his deal with the Knight, he doesn't make any difference between the Knight and Kris, in MANTLE.

-The Knight is an oddly fuzzy being, glitching in and out, unstable, turning into a little cats-eye marble... I wonder if this in and of itself is a clue, if this is not a 'complete' being, but a sort of illusion or construct, something held together with gum and paperclips and string. I could see Kris and Asriel sharing the illusion of the Knight, a role they both exchange, took turns playing. Or perhaps took turns programming as their video game's Final Boss!

-The Knight's head is described as a helmet; the horns need not be literally someone's horns.

-this entire game takes place in the 7 days before Asriel is scheduled to return home "from college". Sounds to me like we are building up to the final event, Asriel's Arrival. Asriel. I think people forget this aspect in almost every single discussion of DELTARUNE and it drives me insane. The entire format of the game is the numbered days before "Asriel's return home". I have to factor this into SOMEthing...

-The voice buried in the code of the game, trapped in darkness, appears to me to be Dess... someone who expresses having not been grateful enough for their life, the simplicity of it... and we know Dess was troubled, fussy, aggro. So I don't believe Dess is the Knight. Though the Knight could be influenced in some way by Asriel & Kris's memories of Dess, as a mutual friend they are both grieving.

The only thing here that relates to Asriel for me, I can't make sense of, but... I'll type it anyway!! That voice trapped deep in the Darkness, describes a door SLAMMING behind them, shutting them in. Ralsei slams closed a Dark world Door in a manner most suspicious and loaded to me, in ch 1. He turns to the audience to do so. Weird emphasis. What does it mean.

To me that hidden text also implies that there is a 'real' Darkness, beneath the reality, beneath everything, but that the present Dark Worlds are not that; they are crudely built on top of it, like a halloween haunted house built on top of a graveyard. They do not reach that Real darkness... but maybe they are, trying to? The voice describes something clawing...
(it could always be that something Kris & Asriel messed with ACCIDENTALLY had the consequence of shutting Dess away... or they could even not know the Magic Asriel tapped into would result in this ?)

So, a lot of those points, for me, don't point to Noelle. My prevailing theory is Asriel/Kris 'are' the 'Knight'. The 'Knight' is a role, not an individual.

So... that's my data. My overall theory for Deltarune is that: Asriel "went off to college", and would talk to Kris every night extensively online, to the point Kris was falling asleep in class (Alphys describes this explicitly!). Godknows if Asriel had some kind of psychotic episode in college, but I think him and Kris devised a Plan (much like Chara & Asriel did in Undertale, but perhaps this time, it is not Chara's plan, but Asriel's ???? idk) and an exact sequence to execute together, The Promise in Our Hearts. This plan required Kris's SOUL and BODY to be split-- the GONERMAKER sequence being Asriel affirming the efficacy of their set-up, testing Kris's SOUL's lack of coherent memories, asking it benign questions like favorite color, flavor, name (Asriel would know the answers Kris would make were all their memories intact. he is also stupid and these are stupid questions a toddler would ask another toddler).

The SOUL is blinded, but the BODY is capable of careful coordinated effort, communicating with the phone individual. So let's imagine that effort is also placed into trading off the illusion of this enemy, The Knight. It's not important it be a real person, it's only important it be an Enemy for everyone to be united to Destroy lol. This plan seems to be rehabilitating Susie, getting Asgore to recognize his own faults, guiding Noelle to a girlfriend... all things Kris & Asriel could want for everyone around them. Improving their lives, at the cost of .... ? Who knows.... but Chara sought to kill themselves in order to free all monsters from the Underground. I don't think the Knight's ultimate goal is 'bad', but it could have heinous consequences in its own way, much like Chara's plan had.

SO uhm. I just don't think Noelle is that intertwined with the very construct of these Dark Worlds, or the execution of this sequence leading to Asriel's Return To Town. She is important in another role of the story, like Susie. Though I'm open to the idea there is some kind of fucked up recursive timeline stuff happening or unknowable magic nobody can predict, even Asriel and Kris. Hubris hubris. The horns on the Knight resembling the Holiday family, could be a charming affect of Asriel and Kris admiring their horns as being cool as kids... or it could be that this was a character Dess drew/played once upon a time, now repurposed by Kris & Asriel (who knows, maybe in an ATTEMPT to draw her back from where she's hidden deep in Darkness, through an effigy of her memories in Asriel and Kris's minds...). Which is modestly Sick & Twisted. Like wearing a costume of your dead friend to evoke their spirit from purgatory.