Gerson Fight Simulator

Keys

This Hammer of Justice fight needs a keyboard. It will not play on a phone. Press Play, then click the game so the keys reach it.

Arrow keys aim the shield and move the heart. Z confirms. C skips the opening scene. Rude Buster wants you to spam Z. There is no WASD and no touch controls.

The build opens on the shop argument, including the line about paying for the axe. C skips that. Then Susie is alone, with a fight menu and a TP bar. The green shield works. You will also see the line about the bells, and the warning that you cannot run while you are green.

The old man

Gerson Boom is Alvin's late father, a historian who became a fantasy author in Hometown. He wrote the Lord of the Hammer series. In Chapter 4, his dust-covered hammer lets a Darkner take his likeness. In the Dark World he is just the Old Man, and he mentors Susie in the Dark Sanctuary.

The Hammer of Justice is his other form, and the Shadow Crystal boss of Chapter 4. He has 1350 HP, defense 0 because he dodges every attack, and attack 15 that scales with the HP Susie has left. The leitmotif is Gerson. The fight is in the Study.

In Undertale, Gerson is the shopkeeper in Waterfall who sells the Torn Notebook. That notebook is one of the items people bring to Undyne the Undying. The link is a light one. The battle in front of you is the Chapter 4 hammer.

How you reach the axe

The golden piano opens the door to the JusticeAxe in the Study. The steps people cite are the ClaimbClaws, then the piano in three parts, then the golden piano. Gerson says the axe costs $999,999,999, and calls that a discount. He offers it if Susie can cut one of his hairs. He dodges her swings, then he transforms.

The fight is optional. You can only do it before you climb the tower at the start of the Dark Sanctuary. Climbing that tower moves the story on, and the door is gone.

Susie fights alone, without Kris or Ralsei. When the heart turns green she asks Kris for help. During the battle he summarises the Lord of the Hammer chapters. She says she wants the story to go on forever. He talks about a white pen of hope.

How to dodge

In the real fight the heart locks in the centre while it is green. Susie's axe is a shield on the side you press. It starts with four directions. Partway through attack 5 the board becomes an octagon, and from then on you need diagonals, which means holding two direction keys. A normal block gives 0.5% TP. Moving the axe, or pressing the same direction again, just before the hit gives 1% TP. You cannot graze while the heart is green.

Spears show up as yellow arrows. The next one to hit turns red with a yellow outline, so watch the red one. The directions in the attack list are the side you block, not the way the spear is flying. Most green waves are the same every attempt, so you can memorise them. His line is that you cannot run while you are green, unless you face the danger head on.

• Coloured shells bounce back and need several blocks. A spinning cyan shell turns 90 degrees counter-clockwise before it returns. Bigger shells are slower.
• A hammer flips the heart to red when it lands, whether it hit you or you blocked it.
• Attack 6: he slashes the board. Step off the middle slash.
• Attack 7: a shell leaves a star trail, bounces, gets spiked down the middle, and rains stars.
• Attack 8: he tilts the board, throws hammers in arcs, then drops a huge hammer down the centre.
• Attack 12: a hammer slams you to the left, then he slashes the middle, the right, and the left. Two of him are a fake-out. A third follows.
• Attack 13: the board is squashed wide and thin. The slashes leave a small safe spot.

There are 21 attacks. Attacks 1 and 2 only appear the first time you play. Attacks 1 through 5 are arrows, slow and then faster, and the board goes eight ways during attack 5. Attacks 6 through 8 are the first hammer turns, and the heart turns red. Attacks 9 through 11 go back to green, arrows plus the first shells. Attacks 12 and 13 are the red slash patterns. Attack 14 repeats attack 8. Attacks 15 and 16 mix cyan shells with arrows and a hammer. Attacks 17 through 19 are arrow storms: circles of arrows, then random arrows that speed up, then a slow dense set. Attack 20 is heavy on shells. Attack 21 throws four shells, including a fast one that comes back for several blocks, then a hammer, then slashes that travel counter-clockwise. Circle near the centre.

You can only win after you survive attack 21. That attack shows up early once he is impressed, at 84 stars or more. OKHeal is worth 9 stars. A Rude Buster you counter-deflect is worth 8, or 6 if the deflect fails. FIGHT is worth 4 stars and 24% TP, so attacking does move the battle forward. Surviving attacks 17, 18, 19, and 20 is worth 30, 24, 24, and 20 stars. DEFEND gives 16% TP, cuts damage by about a third, and gives no stars. He reflects Rude Buster. Deflect it back to stagger him and avoid the damage. A hit is about a third of Susie's current HP, and at least 12 before reductions. He takes your items, so OKHeal is the heal that matters. It gets a little stronger each time you use it, and that boost stays even if you lose.

This fan build covers about 12 of those 21 turns, so the late arrow storms and the final attack may not show up here. Some players say the diagonal blocks are hard or broken, and that a run stuck on the bells line. Others call it a strong recreation. Arrows, Z, and C are the whole control set. Spam Z when you want Rude Buster.

Other fights

The Torn Notebook from his Waterfall shop is a recommended item against Undyne the Undying . Both fights lock you into a green shield.

The Chapter 3–4 sword fight is the Roaring Knight fight simulator .

The same blade in another build is the Black Knife simulator .

Another copy of this hammer fight is on Deltarune Fight .