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Chapter 4Last Updated: 2026-06-28

Deltarune Chapter 4 Walkthrough: The Dark Sanctuary

Complete Deltarune Chapter 4 walkthrough for the Dark Sanctuaries. Solve the gear and clock puzzles, defeat the Jackenstein boss, and unlock the Hammer of Justice secret boss via the Golden Piano puzzle.

Deltarune Chapter 4 ("The Sanctuary") takes Kris, Susie, and Ralsei into the Dark Sanctuaries — a set of three interconnected Dark Worlds born from Hometown's church. The chapter is more atmospheric and puzzle-heavy than its predecessors, with a gothic, eerie tone.

This walkthrough covers the Pacifist Route (Sparing all enemies), the key gear and clock puzzles, the Jackenstein boss, and how to unlock the secret boss Hammer of Justice.

📋 Walkthrough Index

  1. Hometown Day & The Church Dark Fountain
  2. Dark Sanctuary One: Gear & Clock Puzzles
  3. Boss: Jackenstein
  4. Dark Sanctuary Two & Three
  5. Secret Boss: Hammer of Justice (Golden Piano)

1. Hometown Day & The Church Dark Fountain

  1. Sealing the TV Fountain: The chapter opens with Susie and Kris sealing the Dark Fountain from Chapter 3's TV World.
  2. Hometown Exploration: A daytime segment in Hometown. Talk to townsfolk — several carry over hints and recruitment flavor.
  3. The Church at Night: The story moves to the church at night. A new Dark Fountain is opened inside, pulling the trio into the first Dark Sanctuary.

2. Dark Sanctuary One: Gear & Clock Puzzles

Dark Sanctuary One is the first of the three church-based Dark Worlds and is dense with mechanical puzzles.

  1. Gear Puzzles: Rotate and place gears on pegs to power the sanctuary's mechanisms. The goal is to connect a turning gear (the driver) to a target gear so motion transfers all the way through.
  2. Clock Puzzles: Set clock hands to specific times to unlock doors. Clues for the correct times are hidden in the room's decor — paintings, inscriptions, and the position of light beams.
  3. Bookshelf Climb: Near Jackenstein's area, climb the bookshelves to find hidden chests containing Dark Dollars and key items. These are easy to miss.
  4. Shadow Blob Area: An area filled with shadowy blobs. A key item is hidden in the top-left of this zone — collect it for secret boss prep.

3. Boss: Jackenstein

Jackenstein is a major boss of Chapter 4, encountered partway through the Dark Sanctuaries.

  • Phase 1: Jackenstein attacks with heavy, slow-but-powerful strikes and summoned minions. Focus on dodging the big hits and clearing adds when they spawn.
  • Phase 2: Jackenstein becomes enraged and his attacks speed up. Use Susie's Rude Buster and Kris's strongest attacks while keeping HP topped with Ralsei's Heal Prayer.
  • How to Spare Jackenstein: On the Pacifist route, fill the Mercy bar using ACT commands, then Spare to recruit him. Defeating him lethally is also an option but blocks Pacifist recruitment.

4. Dark Sanctuary Two & Three

After Jackenstein, the chapter progresses through the Second and Third Dark Sanctuaries.

  1. Dark Sanctuary Two: More advanced gear/clock puzzles and new enemies. Several chests here hold unique weapons and armor — explore thoroughly.
  2. The Long Climb: A vertical ascent section. Platform carefully and watch for environmental hazards.
  3. Dark Sanctuary Three: The final sanctuary, leading to the chapter's climactic encounter and setting up the story transition into Chapter 5.

💡 Egg Room: Don't forget the recurring Egg Room secret in this chapter. The "Forgotten Man" gives you an Egg — collect it for the cross-chapter Egg collection in Hometown.

5. Secret Boss: Hammer of Justice (Golden Piano)

The Hammer of Justice is Chapter 4's secret boss. It drops a Shadow Crystal, continuing the cross-chapter collection. Unlocking it requires solving the Golden Piano puzzle and gathering a few hidden keys.

Step 1 — Beat the "Funny Boss" First

Before you can fully explore the church, you must defeat the "funny boss" who drops the item needed to access the secret areas. This is a required precursor.

Step 2 — Solve the Golden Piano Puzzle

In the Old Man's study, there is a Golden Piano. Solving this puzzle (playing the correct sequence of notes) is the main trigger for the secret boss encounter.

⚠️ Timing tip: Do this while the Old Man is still sitting in his chair — it's recommended to tackle this as early as possible, before the story progresses past that point.

Step 3 — Gather the Hidden Keys

Two key items gate the path:

  • Waterfall Key: Found behind the waterfall. To access it, donate money into the fountain room (toss money in), then you can cross the water to reach the key.
  • Shadow Blob Key: Found in the top-left of the shadow blob area (Section 2 above).

Step 4 — Fight the Hammer of Justice

With the keys and the Golden Piano puzzle solved, the path to the secret boss opens.

Fight Strategy:

  • The Hammer of Justice hits hard with heavy hammer strikes and shockwave attacks.
  • Constantly attack with Kris and use Susie's Rude Buster; keep Ralsei healing.
  • Defend to manage TP and survive the shockwave phases.
  • Reward: Victory grants the Shadow Crystal.

❓ FAQ (Frequently Asked Questions)

Is Chapter 4 connected to the Weird Route from Chapter 2?

Yes, indirectly. If you completed the Snowgrave Route in Chapter 2, the darker story tone and certain character absences carry over into Chapter 4's events.

Is the Hammer of Justice missable?

Time-sensitive. You should solve the Golden Piano puzzle and gather the keys while the Old Man is still in his chair, early in the relevant section. Progressing the story too far may complicate access.

Do I need all three Shadow Crystals (Ch 1-4)?

They contribute to the cross-chapter Shadow Crystal collection mystery tied to Seam's shop. Collecting all of them unlocks deeper endgame lore.

Where is the Egg Room?

The recurring Egg Room / Forgotten Man appears in this chapter's Dark World. Grab the Egg and bring it to Hometown for the cross-chapter Egg collection.