{"id":342,"date":"2025-10-14T21:37:14","date_gmt":"2025-10-14T21:37:14","guid":{"rendered":"https:\/\/www.yyqiuxia.com\/?p=342"},"modified":"2025-10-14T21:37:14","modified_gmt":"2025-10-14T21:37:14","slug":"deltarune-chapter-4-how-to-fight-hammer-of-justice-secret-boss-guide","status":"publish","type":"post","link":"https:\/\/www.yyqiuxia.com\/?p=342","title":{"rendered":"Deltarune: Chapter 4 – How to Fight Hammer of Justice | Secret Boss Guide"},"content":{"rendered":"

The Hammer of Justice<\/strong> is the secret bonus boss of Chapter 4<\/strong> in Deltarune<\/em> \u2014 and he\u2019s a very different kind of boss. To encounter him in Chapter 4, you\u2019ll need to find three hidden piano pieces<\/strong> to play on the Gold Piano<\/strong> accessed from the Dark Sanctuary Study where the Old Man is found. Defeating the boss gets you a Shadow Crystal<\/strong> and the Justice Axe<\/strong> which is Susie\u2019s strongest weapon so far. This is a tough fight you can only take on with Susie by herself, so you\u2019ll need to practice hard if you want to win. <\/p>\n

Here\u2019s how to unlock the big optional boss in Chapter 4. If you\u2019re still working through earlier chapters, here\u2019s how to earn the Shadow Crystal in Chapter 3, or how to fight NEO Spamton in Chapter 2.<\/p>\n

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Hammer of Justice | Secret Boss Guide<\/h2>\n

The Hammer of Justice<\/strong> boss is found through a secret door in the Study<\/strong> \u2014 the central hub of the Dark Sanctuary in Chapter 4<\/strong>. To unlock the path to the secret room you\u2019ll need to fully explore the first Dark Sanctuary<\/strong> after acquiring the climbing gear<\/strong>. After defeating the Jackenstein<\/strong> boss, you\u2019ll be able to fully explore the Dark Sanctuary<\/strong> area \u2014 don\u2019t progress too far or you\u2019ll lose the chance to find all three music pieces. <\/p>\n

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  • Secret Boss | Chapter 4 Steps<\/strong><\/li>\n
  • Defeat Jackenstein<\/strong> in the Dark Sanctuary World and acquire the climbing gear<\/strong>.<\/li>\n
  • With the climbing gear, there are three optional areas<\/strong> you can now access. Each one has one-of-three parts of a music sheet.<\/li>\n
  • Go to the gold piano<\/strong> above the Study. It\u2019s through the upper door \u2014 then climb the books to the right of the save point.<\/li>\n<\/ul>\n

    The three music pieces<\/strong> you need are located at the top of optional climbing challenges. Reach the top and the music piece will appear \u2014 these pieces DO NOT need to be memorized, and they will appear in the gold piano room. <\/p>\n

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    • First Music Piece<\/strong>: From the Study, go left and follow the path down and left through the magic projectiles. Keep going until you find a climbable wall that leads up \u2014 this takes you to a long climbing sequence that ends with a miniboss. Win the fight to earn the music piece.<\/li>\n<\/ul>\n
        \n
      • Second Music Piece<\/strong>: From the previous music piece, return to the main path (with the magic projectiles you have to dodge) and go right. This leads to a long, stained glass window hallway. After the hallway, there\u2019s a climbable wall that leads to a dark room full of statues. Navigate using sound to find a light switch that makes the second music piece appear. <\/li>\n<\/ul>\n
          \n
        • Third Music Piece<\/strong>: After climbing out of the Jackenstein boss area, return to the save point and go back to the piano puzzle room. In the hallway full of books, there\u2019s a door to the left that leads to a fountain<\/strong> \u2014 go behind the fountain to find a dark path. Climb the wall of bells at the end of the path to reach a second dark passage. That\u2019s where you\u2019ll find the last music piece. <\/li>\n<\/ul>\n

          With all three pieces, go to the gold piano<\/strong> and play the notes that appear. They\u2019ll appear in order once you\u2019ve discovered the three parts. This unlocks the hidden fireplace<\/strong> door in the Study. Going inside and trying to take the Justice Axe<\/strong> will lead to the boss fight. <\/p>\n

          \n

          How To Beat the Hammer of Justice<\/h2>\n

          The battle against the Old Man (the Hammer of Justice) is fought with Susie alone \u2014 equip gear to increase her magic. The Absorb Axe<\/strong> is useful here and boost her defense to maximum<\/strong> with any armor. You CAN NOT damage the boss. You just have to survive<\/strong>.<\/p>\n

            \n
          • The Hammer of Justice will dodge all of Susie\u2019s attacks. DON\u2019T BOTHER ATTACKING<\/strong>. Save all your TP for OkHeal<\/strong> \u2014 your healing is severely weakened, but it\u2019s still extremely useful.<\/li>\n
          • DEFEND<\/strong> every turn to boost your TP. Use OkHeal<\/strong> whenever you can to keep Susie\u2019s health higher. Using attacks or RudeBuster is useless here \u2014 neither will land and they also will not progress the battle.<\/li>\n
          • To progress the battle, you must take actions<\/strong> \u2014 each action will cause the battle to end slightly faster. Attacks are the weakest, Rude Buster is strong, and OkHeal gives the most progress but costs the most TP. <\/li>\n
          • Learning the Hammer of Justice\u2019s patters is the most important skill. Once you can consistently avoid (most) damage, you\u2019ll be able to survive long enough \u2014 use healing<\/strong> whenever you can, attack between heals (if you have the Absorb Axe<\/strong><\/em>) and Defend if you\u2019re struggling to dodge. <\/li>\n<\/ul>\n

            This is a long boss fight that can seem incredibly unfair if you don\u2019t know what to do. Just remember that healing counts towards progressing the boss \u2014 if you only defend and don\u2019t act, the boss will get increasingly difficult until you fail. Your goal is to outlast him and \u201cimpress<\/strong>\u201d him. <\/p>\n

            If you make it to the end of the fight, you\u2019ll earn the Justice Hammer<\/strong> and one Shadow Crystal<\/strong>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

            The Hammer of Justice is the secret bonus boss of Chapter 4 in Deltarune \u2014 and he\u2019s a very different kind of boss. To encounter him in Chapter 4, you\u2019ll need to find three hidden piano pieces to play on the Gold Piano accessed from the Dark Sanctuary Study where the Old Man is found. […]<\/p>\n","protected":false},"author":1,"featured_media":343,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[2],"tags":[283,315,285,55,27,264,10,11,79],"_links":{"self":[{"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=\/wp\/v2\/posts\/342"}],"collection":[{"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=342"}],"version-history":[{"count":0,"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=\/wp\/v2\/posts\/342\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=\/wp\/v2\/media\/343"}],"wp:attachment":[{"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=342"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=342"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.yyqiuxia.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=342"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}