Because of his presence at the Hakuba shrine , he is magically transported into Castlevania alongside all the other characters, and he must be rescued by Soma Cruz
from one of the castle’s boss monsters. Hammer reveals that he has been thinking about quitting the army and opening up his own shop, and he decides to set up a stall at the castle’s front gate to sell Soma powerful items and potions he had found previously for gold that Soma racks up during his quest in the castle. He makes deals with Soma throughout the 2035 event, and he is eventually transported out of Castlevania alongside everyone else once Soma is victorious.
In 2036, Hammer has left the military and is acting as an independent merchant. He locates the giant Castlevania replica constructed by the cult that is after Soma, and Soma soon makes him give that information so that Soma can find the castle and take the fight to them. Hammer follows and decides to set up a shop at the base of the castle much like he did the year earlier, and Soma regularly comes to him to buy the potions and equipment Hammer acquired much like before. Hammer displays a not-so-subtle crush and affection for Yoko Belnades
, who has a shop facing his nearby, and Soma must contend with their concerns for each other the entire game.
Hammer is the only supporting character who does not become playable in the game's Julius Mode, a non-canon scenario which follows the game's bad ending, after Soma is overcome by the power of evil. Fragments of data left in the game imply that Hammer was meant to be playable originally, but the details of his abilities are unknown. It can be assumed, going by Julius Mode's strange reverence for Castlevania III: Dracula's Curse
, that Hammer would have played similarly to Grant DaNasty