Gricard System in the Apocalypse

Alex was still processing the fact that he had been reincarnated into another world in the body of a 15-year-old student, Agnus Vorhells, the youngest son of a baron, when an ethereal voice resounded through the heavens: [Mortals of Havengard, your sins have exceeded quota bearable by the Gods of the Eternal Void. Receive Divine Judgment]. As Havengard evolves with the arrival of the legendary mana, the now Agnus testified that the first kill would drop a spiritual book called Gricard, while the second kill onwards would drop a spirit card. However, after he killed his first zombie, a cold voice echoed in the depths of his soul: [Ding!] [Welcome to the Gricard System!]