Gerson Boom

According to Alvin, Gerson was a "courageous, brilliant, and insightful man." The text on his Memorial Bench suggests that he was welcoming, supportive, and encouraged others to take their time to find inspiration. Since Gerson's writing was inspired by his dreams, this indicates that he had an open mind to new and abstract ideas. According to his former students, Gerson was a somewhat laid-back teacher. He was willing to make up for late students by allowing them to bring him leftover crepes from QC's Diner.

As Darkner, Gerson's personality is reminiscent of his Lightner self. He speaks casually and informally, often using colloquialisms like omitting the "g," reflecting his laid-back temperament. He also prefers to be open-minded, willing to take unconventional paths in favor of new ideas.

Gerson's incarnation as Darkner is also observant, friendly, considerate, and supportive. He has a sense of humor and sometimes feigns ignorance of older stereotypes, both to play pranks and to teach others. In general, Gerson enjoys sharing his wisdom and ideas, and his teaching style focuses on using empathy to uncover the group's strengths; he then indirectly helps by encouraging them to reflect for themselves and consider different options.

Alvin Boom (Son):

Alvin Boom is a turtle-like monster with green skin, pink hair, and eyebrows. He wears a blue robe with what appears to be the Delta rune printed on it, and he can be found outside the church in Chapter 1. A drawing he made while in school, hanging in the unused classroom, depicts his father, Gerson Boom.

Susie (Student)

Jackenstein (Friend)

Gerson is a large, hunched green tortoise with pink eyebrows and a beard, and one yellow eye (the other is completely closed, probably lost). He wears a brown beret and coat, an orange scarf, darker brown trousers, black shoes, and a white shirt with a black tie, giving him the appearance of a scholar. He walks with a green cane.

In the World of Light, it is dust covering an old hammer sealed in a glass display case.

Gerson initially worked as a blacksmith, but eventually decided to dedicate himself to writing. This latter pursuit led him to fame as an author. At first, Gerson became a historian and wrote history books. Later in life, he decided to write stories to entertain his children and published Lord of the Hammer , which became an award-winning fiction series.

At some point, Gerson became a teacher at Hometown's only school. Among his students were Green Fire and Flannel Demon, who would give Gerson leftover crepes to excuse his tardiness.

Some years before Deltarune, Gerson passed away. According to monster lore, a hammer was said to have been buried in Gerson's grave, though Alvin had secretly kept both the hammer and Gerson's ashes in his office, inside a glass case. A memorial bench with a quote from him was also added to the cemetery, and Alphys later replaced him as teacher. Long after Gerson's death, Alvin continued to receive letters of condolence from Gerson's admirers.

As the Hammer of Justice, Gerson trades his typical brown suit for silver armor and armored boots, and sets aside his green cane to wield a giant hammer. Without his hat, Gerson lets his long pink hair fall loose; he remains hunched over, but moves with much greater speed and agility.

In combat, Gerson displays remarkable flexibility for his advanced age: in his resting animation, he continues to kick in the air while carrying his enormous warhammer on his back, and he demonstrates great speed in his numerous attack animations. He appears confident throughout the fight, striking a one-handed handstand while dodging attacks and laughing heartily after his final feint at the end of his finishing attack sequence.

Both the text that appears during battle and the stars above his head indicate his delight when Susie does something that impresses him, primarily by attacking him or using healing magic. This is reflected in the gameplay by linking Susie's attacks and heals to the progression of the battle; the fight lasts longer if Susie neither attacks nor heals. Gerson also deals progressively less damage to Susie as her health decreases, suggesting that he is not interested in winning at all costs.

Attacks

In addition to standard dodge-based attacks, the battle features multiple sections with a green SOUL. Similar to the green SOUL mode in Undertale, while green, the SOUL enters shield mode and cannot move, instead using Susie's axe to protect itself in any direction that is pressed. Notably, the SOUL can defend in eight directions, unlike the four in Undertale.

Each time you change direction (even if you change back to the direction you're facing), the axe "pushes," allowing you to "pause" incoming attacks if you do it at the last second. This produces a different sound and grants you a small amount of TP. It's similar to "grazing" for the green SOUL mode.

Green Soul Projectiles

Arrows: These arrows are aimed at the heart in the center of the screen and must be blocked by Susie's axe. They start with only four directions, but add four more after the first attack. Players using a mouse and keyboard will need to press the two nearest movement keys to tilt the axe. The arrows' speed cannot be changed mid-flight, but they can be launched at different speeds, resulting in the first attack landing last in some salvos.

Hammer: Hammers will appear from above or the sides and must be blocked to avoid damage. After a hammer breaks the axe, the green soul turns red again as Gerson attacks the soul with his hammer, striking vertically or horizontally.

Turtle Shells: After a while, turtle shells will join the volley of arrows. These will bounce off the axe at least once and can only be destroyed when they turn yellow. Although at first they only bounce once and stay in the same direction, in subsequent attacks they bounce twice and shift twice to the left with each bounce.

Red Soul Attacks

Bouncing Shell: A turtle shell flies across the screen, leaving star-shaped projectiles in its wake. After leaving the arena, Gerson will send it flying back into the arena with his staff in the SOUL. This can be done directly towards him or by bouncing it off the floor or ceiling. At the end of the attack, Gerson slams it down across the screen, forcing the SOUL to dodge left or right. Upon hitting the ground, the shell will explode into a shower of star-shaped projectiles that shoot upward and then fall back to the ground.

Hammer Rain: Gerson strikes the arena to the left, tilting it 45 degrees before launching a barrage of hammers into the air, which rain down across the screen. The hammers fall in a roughly straight line, each line marked with a designated space for the SOUL to dodge. After a while, the hammers will increase in size. Shortly after, Gerson hurls one final, enormous hammer into the arena, which can only be dodged by moving left or right.