A character from Undertale, one of the shopkeepers. He is also mentioned in Deltarune with full name of Gerson Boom, deceased author famous for the book series "Lord of the Hammer" and is Father Alvin's father.
He appears in Deltarune Chapter 4, referred to simply as an "old man." He serves as the secret boss and Shadow Crystal holder of the same chapter, under the title "Hammer of Justice".
