This page is an attempt to put together everything I've concluded into a single unified theory. As we only have chapters 1-4, it is obviously incomplete and will always be incomplete until the game is finished. Despite the "grand-unified" title the theory is still pretty disjoint and feels more like a series of incomplete theories, since Deltarune is only halfway finished. I plan on updating this theory as new chapters release, but will probably keep old versions around because it will be fun to see just how much I got wrong.
I will present less evidence than I do on other theory pages, since this theory comprised the conclusions drawn from the evidence on other pages. Instead, I'll link back to those pages when I feel relevant. Presently, the other pages are either non-existent or incomplete, so there will not be much evidence unfortunately.
In case you don't want to read this massive ass page, here is a summary of the salient points.
My understanding of the events in as chronological of an order as possible. Since Undertale and Deltarune are separate universes, events can't be put in a precise order unless they causally affect one another, so I tried to order them according to the point-of-view of Sans assuming he was transported from the Deltarune world to the Undertale world. The focus is on Deltarune so I won't cover a lot of the pre-history of the world of Undertale unless it has bearing on Deltarune. I will probably move this section to its own page in the future as it isn't really relevant to the theory.
There are a lot of characters whose motives are still unclear. This section will be my guesses for them as of Chapter 4.
The eventual goal of the Knight is to cause the Roaring, but they may not want to let it consume the world. My working guess is that they want to summon the Roaring and have the heroes stop it. This explains their odd behavior in Chapters 3 and 4; in Chapter 3, they do not kill the heroes when they have the chance, and if the player wins the fight, there's a bizarre scene where Kris indicates to the Knight through body language to finish things up. In Chapter 4 at the start, if Kris reaches the Knight, they (Kris) refuse to do anything and just stand there and allow the Knight to blast them away. So not only is Kris working with the Knight in some capacity, the Knight chooses not to take out the heroes even when they have a perfect chance to. I believe the Knight is leading the player and heroes on, showing them how to fight them, and then how to defeat Titans, in anticipation of the actual battle against the Roaring. The Knight's identity may say more about their motives, but I am still agnostic on their identity so I will not take it into account here.
On the normal route, while Kris is not directly antagonistic to the player, they take several actions that serve to hide information from the player. In the police station, they refuse to continue reading an article that describes Asgore's firing from the police force. In the Cyber World, they close their eyes before opening the door to Asriel's room. In Chapter 4 at Noelle's House, they stun and trap the SOUL in an attempt to prevent the player from finding the code in Dess' guitar. In the Dark Sanctuary, when Ralsei tells Kris to close their eyes, the player can choose to imagine the Knight. If this is done, Kris begins to imagine the Knight removing their helmet, but switches to visualizing the Jockington in order to not reveal the Knight's identity. This also shows that Kris knows who or what the Knight is. All of Kris' other motives are wrapped up in their past, which we know little about and which I will cover in another page.
Despite him being extremely mysterious, Gaster does state his motives pretty clearly at the end of Chapter 4. He wishes to see Deltarune be completed "WITHOUT ISSUE" and has only ever communicated directly with the player. Similar to what is said about him in Undertale, he seems to exist on a different level than other characters, and is aware of Deltarune as a video game. What he wants from all of it is unknown, but I have two possible ideas depending on whether he's "good" or "evil."
If Gaster is a good guy, then he wants Deltarune to have a happy ending, and all his meta-meddling has been done with that in mind. By patching out the no mercy route (possibly incompletely), he ensures the player will reach a good ending, and even asks them to retry if they fail at certain points in the game. If Gaster is evil (or even just amoral), then he wants to cause the Roaring, likely due to his entanglement with the darkness. By shrouding the entire world in darkness, he'd be able to manifest in an actual physical form, instead of being this abstract force that exists beyond time and space. This makes sense in that it benefits him directly, but also has issues given that Gaster wants the player to try again if they fail on Chapter 1.
I don't know if Gaster factors in the Weird Route; he never comments on the player's actions if they take it, so it's possible he has accounted for the Weird Route in some way, or will take action to prevent the player from completing it.
Her motives are unclear, but seem to involve the Shelter, Dark Fountains, and possibly Dess, with Kris (and possibly Undyne) as accomplices. She also shows an interest in the SOUL bordering on obsession. The following are my predictions for what she's up to. She wishes to summon the Roaring in an attempt to rescue Dess from wherever she is lost in. However, she's not completely insane, so she has a plan to stop the Roaring. Instead, she's only partly insane and wants to use her daughter Noelle as a vessel for the SOUL to fight off the Roaring. Yes, this means she wants the Weird Route, as it comes from her warped interpretation of the Prophecy. However, unlike my Gaster theory, she doesn't necessarily want a no mercy route where everybody gets killed. Instead, she views the Darkners as expendable pawns to be used by the SOUL and Noelle to get stronger. This explains her phone call at the end of Chapter 4 on the Weird Route, where she tells Kris that Noelle is happy to go to the Festival with them. I predict something will happen at the Festival (likely in Chapter 5) that activates Noelle's full potential in the Light World, and allows the SOUL to possess her.
In case it isn't clear, the above means I believe the voice on Kris' phone in Chapter 4 is Carol, and that there is only one voice. The red text is likely for emphasis, since Carol also uses it when telling Kris (or the player?) "YOU are always welcome here."
Asgore's motives seem clearer than Carol's or even Kris'. He wants to prove whatever happened to Dess, clear his name, and get back with Toriel. What is unclear is the extent of his knowledge; he is shown to possess a Black Shard, which presumably came from the Knight, but we know nothing about how he got it or what he knows about The Knight, Dark Worlds, or the Roaring. I will hold off speculating until Chapter 5 since we will probably learn a lot about him there.
The SOUL is usually a stand-in for the player, but there's a possibility the SOUL originally belonged to another human and still retains their motivations. The best candidate is the Vessel created at the beginning of Chapter 1. We don't know anything more than that. Based on the different choices in the game, the SOUL can choose both good and evil deeds. On the Weird Route, their goal seems to be to take over control of Noelle by emotionally manipulating her.
This is one that has a lot of speculation after Chapter 4, but I don't think it's as important as some other mysteries. The consensus seems to be that it's Dess, and I also thought this at first. However, it creates issues from a narrative standpoint that I don't think Toby would abide, so even though the evidence of the Knight being Dess or being connected to her is pretty strong, I don't feel like it is her. Then who is the Knight? I am proud to reveal that I have no idea. The strongest candidates for me are (excluding Dess and in descending order of likeliness): Asriel, Rudy, Carol, Kris' knife, Papyrus, Sans, another Lightner, the Vessel, a Darkner, Gaster himself, Toby Fox/Annoying Dog. I don't really think any of these fit well for various reasons. Instead, I'd like to talk about why I don't think the Knight is Dess.
The strongest candidate for me is Asriel, which has some good evidence but also faces strong narrative problems; the biggest being that Asriel is said to be away at college, but it's also stated he will be coming back for the Festival coming up soon, so perhaps he returned to Hometown early without anybody but Kris knowing, and then started doing Knight stuff. It also explains why Kris and the Knight work together, and why the Knight seemingly imitates Kris' poses - it's actually Kris imitating Asriel. The connections between the Knight and Dess are also due to Asriel's past close relationship with Dess, possibly romantic. If Asriel is the Knight, then he is not permanently stuck in that form, but either takes it in Dark Worlds, or can choose to transform into the Knight when he wishes. Summary of evidence for Asriel Knight:
I could go through the evidence for and against other candidates, but I'd rather withold judgement until either Chapter 5 releases or somebody smarter than me points something out that changes everything. I think it's unlikely we'll get the identity of the Knight in Chapter 5, but there will probably be more hints or evidence that could shrink the list of candidates. Until then, I think the Knight could be Asriel but am remaining agnostic about their identity and not using it in other theories beyond the fact that Kris and the Knight are in cahoots (which could also apply if the Knight is Dess or Rudy).
These are my predictions on the exact relationships between the various characters we see scheming behind the player's back:
An elusive concept only mentioned in a few places, but I believe this is the opposite of the Roaring in a sense. I also think it ties into the Weird Route and the Prophecy. I will cover the Weird Route stuff in another section, and this will focus on just the Prophecy. If the Roaring is an excess of darkness, then the Angel's Heaven is an excess of light. Within the prophecy, here are the mentions of the ANGEL'S HEAVEN in Ralsei's prophecy:
Only they can seal the fountainsAnd in prophecies from chapter 4:
And banish the ANGEL'S HEAVEN.
Only then will balance
be restored,
And the WORLD saved
from destruction.
THEY'LL HEAR THE RING OF HEAVEN'S CALL.
THEY'LL SEE THE TAIL OF HELL TAKE CRAWL.
I interpret "the ring of heaven's call" as the start of the Angel's Heaven, and "the tail of hell take crawl" as the start of the Roaring. Presumably, the Angel's Heaven is used to stop the Roaring, but then must be banished to restore balance.
Outside of the prophecy, the only time something similar (some other characters mention heaven in the general or religious sense, which could be connected but I'm leaving out here) is mentioned is in Spamton NEO dialogue. Some relevant lines below:
[Heaven], are you WATCHING?
* Spamton looks to the heavens.
ARE YOU WATCHING, [Heaven]!? IT'S TIME FOR SPAMTON'S [Comeback Special]!
When Spamton first gains his NEO form, he gives a long monologue where he also references darkness:
WHAT ARE THESE STRINGS!?
WHY AM I NOT [BIG] ENOUGH!?
It's still DARK... SO DARK!
(some lines skipped)
SO BIG WE'LL STAND UP TALL AND SEE PAST THE DARK
STAND UP WITH OUR HEADS IN THE CLOUDS AND LOOK INTO
H E A V E N
The prophecy mentions a need for a balance between light and dark, so it makes sense that too much light would also be dangerous.
The nature and purpose of the Weird Route is explained by the Sword Route in Chapter 3. The original game has been replaced by Tenna with one that follows a single route, and lacks violence (not counting the battle events which happen outside of the game itself). However, by getting S-Rank or Z-Rank and going backstage, Kris can access the original game, referred to internally as the "sword route," and obtain the Shadow Mantle. In the sword route, the player obtains a sword and can kill enemies in combat based on the NES Legend of Zelda. Furthermore, the sword route contains several references to Undertale's No Mercy route and the Weird Route:
My hypothesis is that the Weird Route of Deltarune corresponds to the Sword Route of the Legend of Tenna game, and that futhermore, the Weird Route is the SOUL's attempt to access a No Mercy/Genocide route that has already been patched out of Deltarune, the same way Tenna attempted to patch out the Sword Route. I believe something was done to Kris to prevent them from being able to kill in both the Light World and Dark Worlds, and the Weird Route is the SOUL's attempt to get around that limitation. In Chapter 2, this is done by instead controlling Noelle, and using her ice magic to kill Darkners (and almost kill Berdly). The SOUL chose Noelle both for her potential, given how powerful her magic is, but also for her ability to glitch video games as seen most prominently in the Spamton Sweepstakes blog entries.
Based on this page, I believe the game will end early on the Weird route at Chapter 5, while the normal route continues through all 7 chapters (and anything that may come after). While Toby has said Deltarune will only have one ending, it's possible this doesn't count since it's not a full game ending, or perhaps the game is put in a softlocked state and can never properly end on the Weird Route. This will serve as a message to the player that their choices don't truly matter as much as the characters' choices, and that by trying to meddle so much, they made things worse to the point that the game can't even conclude. Either that, or the game just continues normally. Who can really know with Tricky Tony at the driver's wheel?
It all comes together when it comes to interpreting the Prophecy. A core theme of Chapter 4 is rejecting fatalism, but there's also a through-line of accepting things you can't change. The way I interpret the Prophecy is that it is set in stone for all time, but due to how its written the outcome can be changed by changing one's interpretation of the Prophecy itself. Take the line "LOVE FINDS ITS WAY TO THE GIRL." Within the universe of Undertale, LOVE is a concept that refers to "level of violence," the strength one has gained through mass murder. But it's also a regular English word with almost the opposite meaning. So even if the outcome, "love" finding its way to Suzie (or Noelle), is fixed, the interpretation of what that means can change. With that in mind, lets go through the whole prophecy and try to apply this way of thinking. I will not comment on the obvious parts. Starting with Ralsei's abridged version:
Once upon a time, a LEGEND was whispered among shadows.
It was a LEGEND of HOPE.
It was a LEGEND of DREAMS.
This is the legend of DELTA RUNE
For millenia, LIGHT and DARK have lived in balance,
Bringing peace to the WORLD.
But if this harmony were to shatter...
A terrible calamity would occur.
The sky will run black with terror
And the land will crack with fear.
Then, her heart pounding...
The EARTH will draw her final breath.
Only then, shining with hope...
The heroes are only said to appear when the world is on the brink of destruction, which implies the Roaring needs to happen to even be stopped.
Three HEROES appear at WORLDS' edge.
A HUMAN, A MONSTER, And a PRINCE FROM THE DARK.
Only they can seal the fountains
And banish the ANGEL'S HEAVEN.
This is the first mention of the Angel's Heaven. My interpretation is that it is an apocalyptic event, the opposite of the Roaring, that results when the balance of Light and Dark is broken in favor of Light. Unlike the Roaring, which results in all Darkners being petrified and Lightners left alone in the Dark, the Angel's Heaven would likely be the destruction or petrification of all Lightners as well as the destruction of all Dark Worlds. The Angel is likely the player or SOUL, with the best evidence being the angel decoration falling on top of and covering the SOUL in Chapter 4. Noelle is also particularly connected with the Angel, such as NPCs in Chapter 2 calling her an Angel (including capitalization), her appearance in the Dark World, her room in Chapter 4, and a few other hints. More on that later.
Only then will balance be restored,
And the WORLD saved from destruction.
Today, the FOUNTAIN OF DARKNESS-
The geyser that gives this land form-
Stands tall at the center of the kingdom.
But recently, another fountain has appeared on the horizon...
And with it, the balance of LIGHT and DARK begins to shift...
The rest of Ralsei's version just describes the situation at the beginning of Chapter 1. Now, on to the Chapter 4 Prophecy which has much more to chew on. I will arrange the parts that are out of order into the order I think makes the most sense.
THE PROPHECY, WHICH WHISPERS AMONG THE SHADOWS.
THE LEGEND OF THIS WORLD.
<DELTARUNE.>
A WORLD BASKED IN PUREST LIGHT.
BENEATH IT, GREW ETERNAL NIGHT.
IF FOUNTAINS FREED, THE ROARING CRIES.
AND TITANS SHAPE FROM DARKENED EYES.
THE LIGHT AND DARK, BOTH BURNING DIRE.
A COUNTDOWN TO THE EARTH'S EXPIRE.
BUT LO, ON HOPES AND DREAMS THEY SEND.
THREE HEROES AT THE WORLD'S END.
The start is mostly the same as Ralsei's version. The next lines describe the heroes:
THE FIRST HERO.
THE CAGE, WITH HUMAN SOUL AND PARTS!
Kris' description is very interesting, but not relevant to the bigger theory so I'll leave it for a separate page on Kris in the future.
THE SECOND HERO.
THE GIRL, WITH HOPE CROSSED ON HER HEART.
THE THIRD HERO.
THE PRINCE, ALONE IN DEEPEST DARK
Susie and Ralsei are pretty clearly described. Then it goes on to describe the two apocalypses which may happen:
THEY'LL HEAR THE RING OF HEAVEN'S CALL.
THEY'LL SEE THE TAIL OF HELL TAKE CRAWL.
The first line is about the signs of the Angel's Heaven, the second about the Roaring. When you first trigger the Weird Route in Chapter 2, a unique jingle is played that does resemble ringing in a way. This is what I interpret to be the ring of Heaven's call. Furthermore, I interpret Ralsei's version's mention of banishing the Angel's Heaven to mean aborting the Weird Route. In particular, if the player obtains the Thorn Ring in Chapter 2 but does not equip it to Noelle, they are able to return to the normal route while keeping the Thorn Ring in their inventory. Later on, the Castle Town bakery has an item that can be crafted called the Twisted Sword that requires the Thorn Ring and a Purified Crystal; presumably, the Purified Crystal is created by Seam after giving them all the Shadow Crystals. If I'm correct, then following the prophecy so far requires going onto the Weird Route. Before I say more, the rest of this part of the prophecy:
THE KNIGHT WHICH MAKES WITH BLACKENED KNIFE.
SHALL DUEL WITH HEROES STRIFE BY STRIFE.
(removing irrelevant/joke lines until we get back to the main Prophecy)
THE ANGEL, BANISHED, WILL FINALLY MEET WITH ITS DESIRE.
My interpretation of the Player as the Angel gives a hint as to what their desire might be, since I myself am the Player. It's either a "good" ending, or at the very least an actual conclusion. This fits back into my theory that Chapter 5 will end the game abruptly if the Player stays on the Weird Route. This also confirms that the Angel (or Angel's Heaven) being banished is part of the true prophecy, since up until now it was only in Ralsei's summary. The fact that "it" is used as a pronoun for the Angel makes me think it's, at the very least, not a named character we know; previously I thought the Angel was Noelle but now I think the Angel imagery with Noelle is Carol preparing for her to be taken over by the SOUL/Angel or symbolism for that.
The last part of the Prophecy is worded in a very odd way that I think will become more important, but is unclear now:
AND THEN. WHEN ALL HOPE IS LOST FOR THE TALE
The Prophecy refers to the events as a "TALE" which I feel serves two purposes: it is a meta-reference to Deltarune being a story told as a video game, as well as potentially hinting at fate as something that can be changed. There may also be a pun on the word "TAIL" which is used in several other points (and probably deserves a section on another page eventually). Continuing on:
THE FINAL TRAGEDY UNVEILS.
FOR TO SAVE THE WORLDS, WE LAST OF ALL SAY,
(line never shown in game)
ONLY THEN, WILL THE WORLDS BE SAVED.
Maybe one day I will do a linguistic analysis of the meter and rhymes to determine the missing line, but for now I will only theorize around it. Either way, the Prophecy requires something "tragic" to happen to save "the worlds." This probably refers to the Light World and Dark Worlds together, hence the plural, but could also reference multiple universes. The important thing is that Susie and Ralsei, the two characters we see who know the missing line, don't want it to happen, so it must be something bad. Susie promises to never let it happen, hence the "Broken Prophecy" theory. The Prophecy as it is now requires starting the Weird Route, getting the Thorn Ring, abandoning the route, and then something tragic happening. The player forcing the Weird Route to continue would also go off the Prophecy, and result in the Angel's Heaven ending the world (hence the idea that the game will end early if the player does this). Following the Prophecy would stop both the Roaring and Angel's Heaven, but result in a tragedy.
What would the Broken Prophecy look like? Since the full Weird Route is the Angel's Heaven and the aborted Weird Route stops the Roaring, I'd venture that it results in the Roaring. Furthermore, this is the plan that Kris and the Knight share, hence why the Knight's actions have been to prepare the Fun Gang to fight the Roaring on their own, without whatever boost would be given by the Prophecy. In Chapter 1, the Knight creates the first Dark World next to the closet so that Kris and Susie are forced together and meet Ralsei, and learn how to seal Dark Fountains. Noelle must also be part of the plan, because the Knight created the Chapter 2 Dark World to include her, but the Knight themselves doesn't seem to be involved with the Weird Route. In Chapter 3, things actually veer off plan because Kris creates the Dark World, probably under Carol's orders, and this is the reason the Knight shows up late and attacks the Fun Gang. If you beat the Knight, Kris lets them know through body language that they knew what they were doing, and the Knight kidnaps Undyne instead of Toriel. Chapter 4 is back to Kris and the Knight working together, and the whole chapter is to prepare the Fun Gang to be able to fight Titans.
There are still a lot of things left unexplained, but this page is already massive and all over the place so I'm stopping it here. As food for thought, here are some mysteries/issues relating to this theory:
And things that may be related to the grand-unified theory that we just don't know: