HIGHLIGHTS
- Players must first get three items: the Ice Key, Shelter Key, and Shadow Mantle before unlocking the secret boss in Chapter 3.
- You can unlock these items by playing a console game in the secret room after getting an S-rank in all three rounds.
- After you get the Shadow Mantle, keep playing until the end of the chapter where a special event starts the secret boss fight.
Chapters 3 and 4 came out on June 5, 2025, bringing new enemies, puzzles, and characters you can recruit.
Every chapter has hidden content too, like secret items, rooms, and powerful optional secret bosses.
Players can find a secret boss in Chapter 3 of Deltarune, but it is difficult to locate without following the correct steps.
Deltarune Chapter 3 Secret Boss Guide (No Spoilers)
You first need to play through the chapter until you reach the part where Tenna’s game show begins.
Further, you must earn the highest rank (S-rank) in the first round of the game show. If you fail to reach S-rank, you will have to replay the entire board.
However, if you find it too difficult to reach S-rank, you can buy an S-rank card for 1500 points to guarantee S-rank.
Once you have completed the first round with S-rank, go to the secret room that gets unlocked to get the Ice Key.
Second Game Show Round And Shelter Key
Continue the main story of Deltarune until you reach the second round of the game show. Like the first round, you must earn another S-rank here too.
After you have earned S-rank in the second round of the game show, head back to the room where you got the Ice key.
You will play a different game that primarily involves solving puzzles. In this game, you need to head to the top of the ocean map and enter a hidden door.
Furthermore, players will need to work with a helper to finish the puzzles. At the end, you will get the Shelter key.
Third Round And Shadow Mantle In Deltarune Chapter 3
After getting the Shelter key, you must continue the game until you reach the third round, which leads you to the console once again.
This time, the console game is much longer and has harder challenges than the previous ones you completed before.
At the end of the game, players will be rewarded with the Shadow Mantle. The Shadow Mantle is a key item to unlock and defeat the Chapter 3 Secret Boss.
Further, you need to have space in your armor inventory, or you will not receive the Shadow Mantle. If your storage is full, reload your last save and try again carefully.
How To Trigger The Secret Boss Battle In Deltarune Chapter 3 (No Spoilers)
After getting the Shadow Mantle, keep playing through the chapter like normal until you reach the final section.
Near the very end of the chapter, something special will happen that leads directly to the secret boss fight.
Players will not miss this boss because the event starts automatically during a key part of the final sequence.
If you lose the battle, do not continue to Chapter 4 because reloading Chapter 3 is the only way to try again.
Finally, you will know this is the secret boss when the game changes and allows you to keep retrying the fight.
