Jacob was astounded when he heard 'vampire' from Gracey's mouth. Although he was new to this world, even his old world had stories and legends about vampires. They were the most famous and recognized mystical beings related to blood, especially their legendary, indefinite lifespan, but he didn't know if it was the truth in this place.
However, he wasn't expecting them to be authentic and part of the middle galaxies of the Zodiac Plains, not to mention part of the Dark Beings' dead faction.
Furthermore, Gracey was the daughter of a Vampire Marquis, a legendary king-state dark being. Although he didn't know about the vampire hierarchy, he knew enough not to underestimate them.
Up until now, he had seen many races of Dark Beings, mostly skeletons, zombies, wraiths, wights, midgets, and undead, even ghosts, and knew about their evolution path, but Gracey was the first Vampire he had encountered.