What Are Secret Bosses?
Each chapter of Deltarune hides an optional boss that is significantly harder than the main story fights. These secret bosses are not required to complete the chapter, but defeating them grants powerful equipment and a mysterious Shadow Crystal. They are also some of the most memorable encounters in the game, often tied to cryptic lore.
Shadow Crystals Explained
Every secret boss drops a Shadow Crystal. So far, the full purpose of these crystals is unknown, but Seam and other characters hint that collecting all of them will be important in later chapters. As of Chapter 5, there are five Shadow Crystals to collect.
All Secret Bosses
Jevil
Former Court Jester of Card Kingdom
Jevil is locked in the basement of Card Castle. After meeting a "strange someone," he believes the world is a game and can be defeated either by depleting his HP or by raising his Tiredness to 9 and casting Pacify.
Spamton NEO
The Glitchy Salesman from the Trash Zone
Spamton is a puppet salesman desperate to become a "BIG SHOT." Insert the LoadedDisk into the basement machine in Queen's Mansion to trigger the fight.
Roaring Knight
The Knight of the Dark Fountains
The overarching antagonist appears at the end of Chapter 3. The Shadow Mantle, earned by getting S Rank on both TV Time boards and defeating a shadow mini-boss, makes this fight survivable.
Hammer of Justice (Gerson Boom)
The Undertale Blacksmith Returned
Collect three music pieces across the Dark Sanctuaries, play them on the golden piano, and enter the fireplace path to face Gerson Boom as the Hammer of Justice.
Mad Mew Mew (Pink)
The Possessed Doll
Collect all 10 pink coins in Chapter 5, buy the Mysterious Key at the Cliff Shop, and unlock the pink door near the end of the chapter to face Mad Mew Mew.
General Secret Boss Tips
- Stock up on healing items before attempting any secret boss. Revive Mints, Rhapsoteas, and Scarlixirs are invaluable.
- Save before the fight. Secret bosses are designed to challenge even experienced players.
- Learn the patterns. Most secret bosses are bullet-hell encounters where memorization matters more than stats.
- Equip the best gear. Use weapons and armor from previous chapters or earlier secret bosses to improve your odds.
- Don't give up. These fights are meant to be tough. Each attempt teaches you more about the attack patterns.
Need Help With a Specific Boss?
We have dedicated guides for Jevil and Spamton NEO. The Chapter 5 secret boss, Mad Mew Mew (Pink), is covered in our Chapter 5 walkthrough. Detailed guides for the Chapter 3 and Chapter 4 secret bosses are coming soon.