Released on June 4, 2025, Deltarune Chapter 4 introduces a wealth of new content, including the secret boss, Hammer of Justice!
Developed by Toby Fox (creator of the legendary Undertale), Deltarune is a gripping adventure game full of intriguing mysteries.
One such secret is the Hammer of Justice boss, who’s easy to miss if you don’t know where to look. Luckily for you, we know that RPG secrets and hidden boss fights are what gamers love the most, so use this guide to experience this intriguing encounter!
How to Solve the Golden Piano Puzzle
To confront the Hammer of Justice, you must first solve the Golden Piano Puzzle. To do so, head to Gerson’s study room and go through the top left door. Once there, locate the climbable bookshelf and climb up to find the Golden Piano.
Once you’ve found it, collect three music notes, which you then have to play on the piano in the correct order. That requires a bit of backtracking, but solving this puzzle opens a secret passageway behind Gerson’s desk.
How to reach the Hammer of Justice boss
The passageway will lead you to the secret room. That’s where you’ll find an axe sitting on the desk. Susie will grab it, and Gerson will ask you to pay for the weapon. However, since the price will be too high, he’ll offer to give it to you if Susie can beat his challenge. Accept it, and Gerson will transform into the Hammer of Justice, the secret boss.
Rewards for beating the boss
If you manage to defeat the Hammer of Justice boss, you can expect the Justice Axe and the Shadow Crystal as rewards. If not, Gerson will still offer you these rewards, but Susie will refuse to take them without a rematch.
While the Shadow Crystals you collect from defeating bosses in Deltarune have no use yet, many players speculate they might be required to reach some true ending in the future. Therefore, collect as many as you can and treat them as key items for unlocking upcoming content!