Honestly, playing through Chapter 4 of Deltarune for the first time is a total fever dream. Toby Fox finally dropped Chapters 3 and 4 together in June 2025, and while everyone was busy obsessing over the TV-themed chaos of Chapter 3, the "Prophecy" vibes of Chapter 4 snuck in some of the most cryptic stuff we've seen since the game started. If you’ve just rolled credits and feel like you missed half the game, you're probably right.
There's a lot of noise online. Some people are still looking for a "Snowgrave" equivalent in the church setting, while others are convinced they've found Gaster under a bridge for the tenth time. Let's get into what’s actually there.
The Mystery of the Golden Piano and the Shadow Crystal
The biggest thing people are whiffing on is the secret boss. Everyone assumes it’s going to be like Jevil or Spamton where you just find a key and go to a basement. Chapter 4 makes you work way harder. Basically, you've gotta deal with that golden piano plaque above the fireplace.
You’ll notice it’s missing notes. To find them, you actually have to backtrack through the "Sanctuaries" (the main dungeon areas of Chapter 4). Most players just rush forward because the shadowball enemies are a massive pain to dodge, but if you look behind the bookcases in the third sanctuary, there's a literal hidden path. It leads to a room that looks like an old aqueduct.
If you talk to the Organikk NPC there and tell him you "haven't forgotten," he gives you a sequence. You take that back to the piano, play the song, and that's how you unlock the path to the real heavy hitter of the chapter.
Who is the Secret Boss?
There's a lot of debate here. In Chapter 3, we had the whole "Shadow Mantle" questline involving the S-Rank rooms and that weird "Mantle" boss that drops the Shadow Crystal. In Chapter 4, the secret boss is tied much more closely to the lore of Hometown. Some fans call him "The Collector," but the game files and the Shadow Crystal drop suggest something much more tied to the "Prophecy" glass we see throughout the chapter.
When you beat him—and good luck, because his "Meteor" phase is a nightmare—you get a piece of equipment that makes Kris’s soul move faster. It’s basically a permanent speed buff for heart-mode.
Finding the Chapter 4 Egg
Toby isn't stopping the egg tradition. It’s become a bit of a meme, but the Chapter 4 Egg is tucked away in a spot that most people walk right past. When you’re in the room with the flying books—right before the shadowball gauntlet—there's a section of the wall on the right that doesn't have a collision box.
Walk through it. You’ll end up in that classic "room between rooms." The Man is there behind the tree, as usual. If you have the eggs from Chapters 1, 2, and 3, something different happens when you talk to him this time. He doesn't just give you the egg; he mentions "the pile is growing."
The Weird Route (or Lack Thereof)
Is there a "Snowgrave" in Chapter 4? This is what everyone asks.
Short answer: Not really, but also yes.
In Chapter 3, you could do the "Ice Key" questline in the backstage minigames, which felt very much like an alternate route. In Chapter 4, the "weirdness" is more about who you bring with you. If you’ve been "recruiting" everyone and playing a perfect pacifist run, the Town Square in the Dark World looks like a paradise. But if you’ve been violent, the NPCs start treating Kris like a monster.
There is a specific interaction with the "Hammer of Justice" item. If you use it to "smash" certain environmental objects in the church-themed Dark World instead of solving the puzzles, the music shifts. The atmosphere gets heavy. It doesn't trigger a full-blown alternate ending like Chapter 2, but it clearly flags your save file for something big in Chapter 5.
Small Easter Eggs You Definitely Missed
- The Sink Mystery: If you check the sink in the Light World after the chapter, the dialogue has changed. It no longer says "the sink is clean." It says "it’s waiting."
- Sans's Grocery Store: If you go to see Sans, he mentions a "brother" again, but this time he says he’s "busy at the festival." The 2026 release of Chapter 5 is heavily hinted to take place during this festival.
- The Onionsan Secret: Go back to the lake. If you talk to Onionsan after finishing Chapter 4, he mentions hearing a "song" coming from the seafloor. This actually matches the notes you had to play on the golden piano.
What to do next
If you've finished the chapter, your priority should be the Shadow Crystal. Seam (the shopkeeper from Chapter 1) has new dialogue once you bring him the crystals from Chapters 3 and 4. He’s starting to look worried.
Make sure you’ve recruited everyone. Chapter 5 is confirmed for the second half of 2026, and Toby Fox has hinted in his newsletters that the "Castle Town" population will determine how the festival in the Light World plays out. If your town is empty, you’re likely going to have a much harder time.
Actionable Steps:
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- Backtrack to Sanctuary 3 and find the hidden path behind the bookcases to get the piano notes.
- Defeat the secret boss to obtain the speed-buff equipment and the fourth Shadow Crystal.
- Check the Lake in the Light World to trigger Onionsan's new dialogue about the seafloor song.
- Save your game in a separate slot before starting a "violent" run to see how the Town Square changes.
By the time Chapter 5 rolls around, these small flags are going to matter. Toby doesn't put "useless" dialogue in the game—everything from the sink to the piano is building toward the finale.