Deltarune Chapter 4 100% Walkthrough Guide - All Items, Secrets, Bosses, and Golden Piano Puzzle

⚠️ Disclaimer: This guide is based on datamined information and predictive analysis of Deltarune Chapter 4, which has not been officially released. All details, including dates, mechanics, and story beats, are speculative and may change upon final release. Proceed with caution and treat this as informed speculation, not confirmed fact.

With Chapter 5 expected to arrive as a free update (projected June 24, 2026 based on current development timelines), there has never been a better time to ensure your save file is as complete as possible. Chapter 4 marks a dramatic tonal shift from its predecessor’s minigame-driven chaos, delivering instead a sprawling, traditional RPG structure spread across three unique Dark Worlds and an expansive Light World. It also houses some of the most intricate puzzles, missable collectibles, and challenging secret boss encounters Toby Fox has designed to date. This guide covers every concealed item, the Golden Piano Puzzle, the Hammer of Justice boss, all Shadow Crystals, the Weird Route continuation, and hidden nooks like the Egg Room. Follow it step by step, and you will step into Chapter 5 with a thoroughly completed adventure ready to carry forward.

Story Progression & Missable Items in the Light World

Chapter 4’s narrative unfolds across multiple Light World locations: Kris’s hometown, Castle Town, the church, Noelle’s house, The Old Man’s Study, and the Northwest Library. The core story involves investigating the church, navigating Soul Stealth segments, and ultimately confronting a Titan after the Knight creates a Dark Fountain inside the Third Sanctuary. The chapter also introduces new cut-content remnants for diehard completionists, such as early versions of Ribbick’s CroakOn and CroakOnX acts, which are believed to require timed C-presses rather than mashing. This information comes from datamined game files and may not appear in the final release.

⚠️ Missable Light World items are tied to specific story beats and optional conversations. For example, secret fountain items can be obtained only during the initial exploration of certain Sanctuaries. If you rush through story triggers, you may lock yourself out of consumables that affect dialogue in later chapters. The recommended approach is to thoroughly search every room before speaking to key NPCs, especially in the church and Noelle’s house. Completing optional conversations with townsfolk also unlocks small flavor text that carries into Chapter 5, so leave no stone unturned.

All Collectibles, Shadow Crystals, and the Egg Room

The Chapter 4 collectible hunt is divided into three main categories: Shadow Crystals, Golden Leaves, and hidden consumables unique to each Dark World.

Shadow Crystals are the most critical long-term items. Gathering all of them across the three Dark Worlds and the Light World is widely believed to be a prerequisite for any potential hidden ending that may span the entire Deltarune saga. The crystals are often tucked behind optional puzzles or guarded by minor enemies. A complete list:

• First Dark World: Behind a locked door in the Gallery of Ancient Faces. The key is obtained by solving a pipe-organ puzzle in a nearby alcove.
• Second Dark World: Inside a treasure chest on a balcony reachable only after activating a series of pressure plates in the correct order.
• Third Dark World: Dropped by the Hammer of Justice (more on that below).
• Light World: Found in The Old Man’s Study, hidden inside a bookcase that requires a specific code from a note in the church basement.

The Egg Room returns as a delightful secret. To access it, walk to the 100th window from the left in the long hallway past the four Organikks. Entering that window transports you to a quiet room containing an Egg. As with previous chapters, re-entering this room opens a passage to a secret tree room that holds a unique consumable. Make sure to grab the Egg before leaving, it has appeared in every chapter so far, and its purpose continues to deepen.

Other hidden collectibles include Golden Leaves, which are scattered across each Dark World. They serve no immediate gameplay function but unlock supplemental lore entries in the game’s journal. The optimal exploration order to minimize backtracking is: First Dark World → Light World (church, study) → Second Dark World → Third Dark World → Egg Room after exiting the final Dark World.

Golden Piano Puzzle & Hammer of Justice Secret Boss

The Golden Piano Puzzle is the gateway to Chapter 4’s most challenging optional content. Solving it requires collecting three hidden music sheets, one in each Dark World. The sheets are not immediately obvious; they are tucked inside breakable objects, behind NPCs who will move only after certain conditions are met, or at the end of optional platforming challenges.

• Sheet 1: Located in the First Dark World, inside a cracked statue in the Gallery of Ancient Faces. Interact with the statue after defeating all enemies in the room.
• Sheet 2: In the Second Dark World, given by a ghostly NPC who appears only after you have completed a side quest involving lost memories.
• Sheet 3: In the Third Dark World, found at the base of a spiked pillar. Use a character with the “Freeze” ability to create a platform and reach it safely.

Once all three sheets are in your inventory, return to the church’s third floor, where the Golden Piano awaits. Play the notes in the order indicated on the sheets, the melody is a subtle reference to Undertale’s “His Theme.” A successful performance unlocks a hidden staircase.

Below lies the Hammer of Justice secret boss. This entity is a Shadow Crystal boss, a Darkner formed from mementos of Gerson (the old shopkeeper from Undertale, known here as “The Old Man”). The battle is an endurance test: the Hammer of Justice has high defense (estimated HP range: 3,500, 4,200 based on datamined values) and attacks with pattern-based hammer swings and shockwaves.

Attack patterns and tells: The boss has three phases. In Phase 1 (100%, 67% HP), it alternates between a wide hammer slam (dodge by staying near the center of the battlefield) and a horizontal shockwave (jump over it). In Phase 2 (66%, 34% HP), it gains a vertical shockwave that requires precise positioning between gaps, and begins summoning small debris that falls from the ceiling. Phase 3 (33%, 0% HP) introduces a rapid flurry of overhead hammer swings, each telegraphed by a brief flash on the hammer’s head. It also gains a rage mode that increases attack speed by 20% below 15% HP.

Recommended strategy: Bring Susie for raw damage and Ralsei for healing. Kris should use items that boost attack power (e.g., Power Popcorn or Apple Juice). The boss is weak to fire-based magic, torch spells or Ralsei’s upgraded healing can exploit this. Survival fallback: If underleveled, equip Ralsei with the “Pacify” ability to temporarily stun the boss for two turns, allowing a free heal round. Use Ralsei’s Dual Heal every three turns to keep the party above 70% HP. Save TP for Act combos (Susie’s “Rude Buster” deals heavy damage in Phase 3). Exit strategy: if the party is wiped, return with the “Revival Mint” item from Castle Town to avoid losing progress on the puzzle.

Defeating the Hammer of Justice rewards you with a Shadow Crystal, a unique weapon (the “Justice Hammer,” a powerful weapon for Susie), and armor with high defense. Moreover, the lore text obtained after the fight hints at the nature of the Titans and the Knight’s true plans.

Weird Route (Snowgrave Continuation) & Preparing for Chapter 5

Chapter 4 continues the Weird Route from Chapter 2’s Snowgrave events. To trigger it, you must have completed the Snowgrave route in Chapter 2 (defeating Spamton NEO and freezing Berdly). In Chapter 4, the altered story begins during the church investigation. After Kris rips out their SOUL, Noelle, free from Susie’s distracting influence, invites Kris to her room privately instead of the usual group study session.

On this route, dialogue is darker, certain NPCs disappear, and boss encounters become more difficult. The Titan fight is replaced with a variant that targets Noelle specifically. If you intend to experience both routes, maintain separate save files before the church segment.

Checklist for a fully-completed save file:

• Collect all Shadow Crystals (4 total).
• Solve the Golden Piano Puzzle and defeat the Hammer of Justice.
• Obtain the Egg from the Egg Room.
• Complete the normal Pacifist/Neutral route and the Weird Route separately (ideally in different save slots).
• Collect all Golden Leaves and optional consumables.

Datamined evidence suggests that player choices across chapters will impact the ending, though Toby Fox has not officially confirmed the full scope of this mechanic. While the exact nature of any hidden ending remains unclear, collecting every Shadow Crystal and defeating the secret boss is widely believed to be a prerequisite (based on leftover game scripts and variable flags). With Chapter 5 arriving in record time, investing the effort now ensures that your save file carries as much weight as possible into the next chapter.

Stepping into Chapter 5 with a Complete Save

Deltarune Chapter 4 is the halfway point of this seven-chapter saga, and it is packed with secrets that reward patience and multiple playthroughs. By following this guide, tracking down every Shadow Crystal, solving the Golden Piano Puzzle, conquering the Hammer of Justice, and exploring the Weird Route, you will have a pristine, thoroughly completed save file ready for the free Chapter 5 update (projected June 24, 2026). Toby Fox has promised the fastest turnover yet, so there is no excuse to leave any content behind. Every decision, every collectible, and every hidden encounter matters more than it seems. Good luck, and enjoy the next chapter of the adventure.