Keep losing to the Hammer of Justice? Learn exactly how to fight Gerson in Deltarune Chapter 4. Find the best gear, dodging tips, and hidden mechanics to win!
Are you getting constantly wiped out by the Hammer of Justice? If you are struggling to survive the intense barrage of attacks in Deltarune Chapter 4, you are definitely not the only one.
With the recent global release of Deltarune Chapter 5, thousands of players are backtracking to secure their Shadow Crystal. You will want this crucial item in your save file before carrying your progress over into the new content. But standing in your way is Gerson Boom—reborn in the Dark World as the Hammer of Justice—and he does not go down easily.
This guide will walk you through exactly what you need to know. From solving the pre-fight puzzles to mastering a hidden low-HP mechanic that changes everything, you will find the practical strategies you need to win.
Where to Find Gerson: Unlocking the Chapter 4 Secret Boss Arena
Unlike Jevil or Spamton NEO, reaching Gerson requires some significant backtracking and exploration. The game will drop a few hints, but here is exactly how to unlock his arena.
- Retrieve your gear: First, you need to progress far enough in the main story to acquire the climbing tools from Jackenstein.
- Backtrack to the sanctuary: Return to the Old Man’s Study located in the First Sanctuary.
- Solve the puzzle: Use your new climbing tools to scale the walls near the study (specifically the book paths). You will need to explore the adjacent Dark Maze and library areas to find scattered musical notes. Use these notes to complete the Golden Piano puzzle, which will finally unlock the door to the hidden boss arena.
Gear Up for Survival: The Best Equipment for the Gerson Boss Fight
Gerson hits incredibly hard. If you are wearing standard mid-game gear, you are going to have a rough time surviving his later phases. Equipping the right items can make or break this encounter.
We strongly recommend equipping the Shadow Mantle. Because Gerson’s attacks are heavily coded as Star or Dark elemental damage, this specific armor drastically reduces the damage you take.
Additionally, before you leave the Golden Piano puzzle room, make sure you grab the AbsorbAxe (sometimes referred to by players as the Vampire Axe) from the nearby chest. Equipping this on Susie allows you to heal slightly while attacking, which is a massive advantage since you are fighting him solo and item usage is restricted.
Taming the Hammer of Justice: Your Core Battle Strategy
The Hammer of Justice requires a completely different approach compared to the Roaring Knight or standard enemies. Here is how you can tilt the odds in your favor.
Master the Low-HP Sweet Spot
One of the best-kept secrets of this fight is how Gerson calculates his damage. Gerson actually deals less damage when Susie’s health is low. If you are constantly topping off your health bar, his hits will be punishingly strong.
Instead of panicking when you take a hit, try keeping your health around 50 HP. This gives you a safe buffer to survive an error while preventing his maximum damage output from triggering.
Progressing the Fight Fast
The goal of this encounter isn’t just to deal damage; you need to generate star particles to advance his dialogue and progress the story.
To speed this up, use regular attacks and Susie’s “OK Heal” command to keep the fight moving forward. A great hidden feature here is that “OK Heal” actually improves and heals more the more you use it. Try to avoid over-defending. While guarding feels safe, it actually slows down the progression of the battle and forces you to survive more attack cycles.
Should You Use Rude Buster on Gerson?
You might have noticed the Rude Buster ping pong interaction. Deflecting his attacks with Rude Buster looks incredibly cool and definitely speeds up the early phases of the fight. However, doing this comes with a major catch: it makes his late-game patterns much faster and harder to dodge.
If you want to survive the final phases, limit your use of Rude Buster to a maximum of three times per attempt.
Master the Movement: How to Dodge Gerson’s Brutal Hammer Attacks
If you are getting a “Game Over,” it is probably happening during his massive hammer-throwing phase or the confusing “blue shell” whirlpools. Try these movement strategies to stay alive:
- Find the Safe Zone: When the screen fills with heavy hammer barrages, immediately move toward the middle of the top-right side of your screen. This specific spot often hides you from the largest hitboxes once the smaller projectiles pass by.
- Change Directions: Stop moving side-to-side horizontally. Start moving diagonally through the gaps. The awkward angles of his hammers are much easier to slip past when you move on a slant.
- Learn the Rotation: Spend a few “throwaway” attempts simply memorizing his standard attack patterns. Study which side of the screen his whirlpool arrows spawn from first. If you learn the early patterns, you will enter the brutal late-game hammer phase with plenty of health to spare.
Quick Answers to Your Gerson Boss Fight FAQs
Do I need to beat Gerson for Deltarune Chapter 5? While beating him is completely optional and not required to start Chapter 5, you really want that Shadow Crystal carry over. Defeating him also triggers some massive lore drops regarding his son, Father Alvin, and the Hometown graveyard. If you care about the game’s deeper story, this fight is a must-play.
How to get max TP against Gerson? To generate TP quickly, you need to master the “perfect block” mechanic. During his arrow attacks, use your movement keys to actively shift Susie’s shield. Timing your directional blocks perfectly against the incoming arrows rewards you with a massive bonus to your TP gauge, allowing you to use “OK Heal” more frequently.
Final Thoughts
Toby Fox designed the Hammer of Justice to test your patience and your reaction speed. But with the Shadow Mantle equipped, careful health management, and a little practice dodging those hammers, you absolutely have what it takes to win.
Sources & Community Strategies: Many of the unique combat strategies and dodging patterns featured in this guide—including the low-HP mechanic and safe zones—were crowdsourced from the dedicated Deltarune community. For more player discussions and alternative tips, you can check out this Reddit thread.
Have you managed to beat Gerson yet? Which of his attacks gave you the most trouble? Share your experience and any extra tips you have in the comments below!
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