If you just finished the second part of gaming auteur Toby Fox’s follow-up to the highly acclaimed indie game “Undertale,” you’re probably wondering what you just saw in the ending sequence.

“Deltarune’s” second chapter released Sept. 17, three years after the first chapter. I could just write a regular review of “Deltarune,” an “Earthbound”-inspired game that is split into seven parts with a battle system where you can win over the hearts of your enemies instead of killing them. I could talk about Chapter 2′s incredible music and engaging characters, how it fixes the issues Chapter 1 had with story pacing, and how it introduces a villain that’s actually good this time (Queen is possibly my favorite villain of all time). But anyone who’s a fan of “Undertale” or the Earthbound games will probably end up playing “Deltarune” Chapters 1 and 2 anyway.

Instead, I’d like to talk about what’s happening in the story, which is loaded with convoluted lore and back-to-back twist endings. It may be unwise to speculate about the future of a game with five upcoming chapters — and one that prides itself on twists and subversion — but there’s enough evidence in “Deltarune” and “Undertale” to piece together some plausible theories.

The following is an explainer filled with heavy spoilers for the superfans and those interested in getting deeper into the hidden story of “Deltarune.”

What’s the story so far?

In Chapter 1, players are prompted by a mysterious voice to create an avatar for the game. Then, the avatar is thrown away. It’s the first indicator that “Deltarune” is different from “Undertale,” a game that prominently featured player choice — including the ability to get through the game without killing a single enemy. In “Deltarune” Chapter 1, conversely, your choices don’t matter.

You’re forced to play as a preset character, Kris, and introduced to an alternate universe version of “Undertale’s” world. “Deltarune” is also populated by monsters, and it includes “Undertale’s” main characters like Toriel, your mother, and Asriel, your brother who recently went off to college. These alternate versions of the characters don’t remember the events of “Undertale,” and some of their traits are different, like Undyne’s lack of an eye patch.

You learn that this universe has two realms: the “Light Realm” populated by Lightners, and the “Dark Realm” populated by Darkners. The Dark Realm is actually a series of worlds created from Fountains of Darkness, which only Lightners can create in the Light Realm. Both chapters involve Kris and a friend named Suzie, both Lightners, and a Darkner named Ralsei (who looks suspiciously like your brother Asriel) entering one of these Dark Realm worlds and sealing up a Fountain of Darkness. This causes that world to disappear, which is good: If too many Fountains are created, not only will all Darkners turn to stone, but the Light Realm will experience “The Roaring,” an event where giant Titans will come to ravage the land.

A key mystery animating the game is figuring out who is creating these Fountains of Darkness. By Chapter 2′s ending, it’s revealed that this person is actually Kris. After inviting Suzie to their house for a sleepover and waiting for her and Toriel to fall asleep, Kris pulls a move they also do at the end of Chapter 1, albeit partially off-screen: They rip their heart out of their chest — effectively removing the player’s control — and create a Fountain of Darkness right in the middle of the room, which envelops everyone.

What’s the meaning behind Kris ripping out their heart?

In “Undertale” and “Deltarune,” the red heart is a stand-in for the player themself. That heart is the icon used in battles, menus and dialogue choices. So whenever Kris rips their heart out, it’s the game effectively saying, “You’re no longer in control of Kris.” This is most evident in Chapter 1′s ending, where you can actually move the heart after Kris rips it out.

What’s Kris’s plan?

They’re purposely attempting to bring about The Roaring. There are two possible motives for this.

The first: It’s hinted multiple times how much Kris misses their brother, Asriel. When they were little, the game explains, they’d play “Dungeons and Dragons”-like games not dissimilar from the experiences the Dark Realm worlds bring. So there is a very likely chance that these Dark Realm experiences are simply taking place in the characters’ minds, and Kris attempting to bring The Roaring is simply them not willing to let go of the cherished experiences they used to have with their brother.

In this possibility, Ralsei — an anagram for Asriel — is a manufactured character in Kris’s mind created because they wish to relive those experiences with their brother. It’s why Ralsei looks like Asriel. This also explains why Ralsei doesn’t turn to stone after entering Chapter 2′s Dark Realm world, despite the fact that Darkners of one world can’t exist in another. Ralsei’s simply not a Darkner.

Finally, this also explains a weird event at the beginning of Chapter 2, where the Chapter 1 Darkners in Ralsei’s world don’t appear until you bring cards, toys and stuffed animals. These items closely resemble those Darkners themselves and were in the Light Realm room you found yourself in after sealing the Fountain of Darkness in Chapter 1. This event implies that the Dark Realm experiences are imagined in the characters’ minds, sort of like a “D&D” session.

This brings us to our second possible motive, which could still exist with the first: Kris is not who we think they are. Ever wonder why their green-and-yellow striped shirt looks so familiar? What about Kris’s knife and their violent tendencies after they rip out their heart?

Maybe Kris is secretly Chara, the result of Gaster’s experimentations with “Determination.”

What. Are. You. Talking. About. Chara? Gaster? Determination?

Chara is a character who only shows up during the genocide route in “Undertale,” where you purposely kill every enemy in the game. Their weapon of choice is a knife, and they have glowing red eyes, so it’s not difficult to draw parallels between them and Kris.

In “Undertale,” it’s presumed that either (a) Chara is someone that exists in the game’s world before the events of “Undertale” take place, or (b) that Chara is a physical embodiment of the actual player’s lust for power (which manifests by gaining levels after defeating monsters).

Your killing spree “awakened [them] from death, [their] human soul,” Chara says. “Our plan had failed, hadn’t it? Why was I brought back to life?”

This implies Chara was part of some unknown plan, and “Deltarune” might be hinting at whose plan it was: Gaster’s. Gaster is the biggest lore rabbit hole that the “Undertale” series has to offer. He’s a hidden character that doesn’t appear in the story and only speaks in Wingdings. However, by digging through “Undertale’s” code and tweaking background values, you can find the character in-game alongside a bunch of surrounding information.

Gaster is a scientist experimenting with Determination, an energy source found in humans that allows them to defy predetermined patterns that the universe dictates they must follow. In short, Determination is a metaphor for a player’s agency or choices in video games. In the series’s universe, it’s something that only certain characters, like the actual players themselves, possess.

So remember that mysterious voice in Chapter 1 that made you create that avatar? This could very well be Gaster attempting to create Chara as part of an experiment to see the effects of Determination. This also explains a mysterious red bunker you find hidden in Chapter 1. That’s very likely Gaster’s hiding spot: When you interact with the door, it produces the same sound that Gaster does according to the “Undertale” files. (Click the links at your own peril; these are not pleasant sounds).

This sound is described in “Deltarune” as “garbage noise,” the word-for-word description that a character in Chapter 2 explains that their friend heard before they went insane. Was the call something that clued them in to their world being an experiment, causing their insanity?

Perhaps Fountains of Darkness are simply experimental playgrounds that Kris/Chara creates in order for Gaster to test the effects of Determination. This would also explain why the player can actually make choices that change the story in Chapter 2.

Wait, choices are back?

Sort of. There’s an optional route in Chapter 2 similar to the genocide route in “Undertale.”

In this route, you force Noelle, a Lightner companion, to kill everything in that chapter’s Dark Realm world, including Berdly, another Lightner companion. It’s dark, disturbing and seems to forever corrupt Noelle. But it also plays into the theory of Gaster’s experiments with Determination.

Remember, Determination is basically player choice. “Deltarune” Chapter 1 didn’t have any choices that the player could make that would meaningfully change things, but in Chapter 2, player choice slowly reenters the picture. It’s almost as though Gaster is altering variables, using Chara to see the effects of Determination, bringing player choice slowly back into the series, chapter after chapter.

Of course, this “experiment” involves Kris/Chara creating Fountains of “Darkness,” right? One of Gaster’s journal entries players found in “Undertale” reads: “DARK DARKER YET DARKER. THE DARKNESS KEEPS GROWING. THE SHADOWS CUTTING DEEPER. PHOTON READINGS NEGATIVE. THIS NEXT EXPERIMENT. SEEMS VERY. VERY. INTERESTING.”

Doesn’t this imply that “Deltarune” isn’t in an alternate universe from “Undertale”?

The game’s creator told Variety that “Deltarune” isn’t a sequel, and that, “What you’re seeing [in ‘Deltarune’] is not the world of ‘Undertale.’”

Here’s the bombshell, though: I believe “Deltarune” is a prequel to “Undertale.”

If that’s the case, Chara will likely succeed in summoning The Roaring, leaving Lightners to fight the Titans. Not only is “The Roaring actually happens” a plausible final chapter — a role-playing game needs to ramp up the stakes at the end, after all — but it also perfectly sets up the story of “Undertale.”

“Undertale,” in a sense, is the ultimate experiment for Determination. We already know how big of a role player choice plays in that game. Additionally, no Darkners exist in “Undertale” because The Roaring turned them all into stone, something Ralsei explains is a consequence of the event.

So at the end of “Deltarune,” perhaps the universe gets destroyed, and the remaining pieces make up the universe of “Undertale.” This would explain why certain character aspects are different (maybe Undyne loses an eye in The Roaring, for example) while other aspects remain the same (Toriel and her ex-husband Asgore are still broken up; Sans and Toriel still have their pun thing; and Alphys is still attracted to Undyne). It would also explain “Gaster Followers”: “Undertale” characters who are grayed out versions of “Deltarune” characters spouting bleak, unexplainable dialogue.

Is there more evidence for this theory?

Sans is all the evidence you need.

Sans is a character who mysteriously seems to be aware that “Undertale” is a game. He exhibits a deep, fourth-wall-breaking knowledge of the confines of the game, expressing capabilities similar to the player’s abilities with Determination. He also says strange things in your in-game fight with him like how he “gave up” on “trying to go back” to a particular place. Since he clarifies that this isn’t the Surface, is this place the “Deltarune” universe, and are Sans’s memories of “Deltarune” still intact?

Finally, in “Undertale,” you’ll find a room behind Sans’s house with items that the game’s fan community still hasn’t found good explanations for. There’s a police badge (possibly Undyne’s police badge from “Deltarune”), blueprints (they match the blueprints of a machine you build in “Deltarune” Chapter 1), and a photo album of Sans with a bunch of unrecognizable characters. If you come back here after beating “Undertale,” the interactive text for this photo album changes.

And what’s the name of the song that plays at the end of “Deltarune” Chapter 1? “Don’t Forget.”

What’s going to happen in the next few chapters?

We don’t know when exactly the remaining five chapters will release, but they’ll probably follow a similar format to the other two: Kris and Suzie get sucked into another Fountain of Darkness world and need to seal it with a guest-of-the-week character from the Lightner town. With Chapter 2′s ending in mind, the Chapter 3 character is without a doubt Toriel.

We also know that Undyne is on her way to Kris’s house since Toriel asked her to come after her tires were slashed. Whether Undyne is grouped with Toriel in Chapter 3 or if she gets her own chapter is still up in the air, but it excitingly seems like the “Undertale” alums will feature more prominently in the upcoming chapters.

Regardless of where Fox takes the story next, “Deltarune” is shaping up to be as mind-blowing of an experience as “Undertale” was. The next chapter is bound to be, in Gaster’s words, “VERY. VERY. INTERESTING.”

Read more: