

As the Monster Age arrived and special abilities awakened, what awaited humanity was the end of the world. At the brink of the apocalypse, Frank Channing was sent back in time to the second year of the Monster Age. There, he awakened the Infinite Devouring System, allowing him to gain growth points by hunting the monsters. Along with it came a mysterious serpent-shaped mark on his arm. It could transform him into a powerful serpentine creature capable of wielding the very forces of the monster—seemingly tied to the secrets of the Blood Moon. From the system, Frank learned that he carried the mission of saving the world.

Richard, a broke, sharp-tongued black-market vet, gets evicted from his rundown flat and is hired at an astronomical rate by the mysterious noblewoman Catherine to be the night keeper of Ashford Manor. His plan is simple: coast through the shift, collect his paycheck, and get out. But when he stumbles into a forbidden zone to save a mortally wounded Abyssal Royal Squid, he inadvertently completes the seal on an S-class calamity—and the overflow magic floods straight into him. Suddenly, the entire world thinks some legendary hidden powerhouse just obliterated the disaster. He keeps healing beasts for the money, but the more he heals, the stronger he becomes, earning him an A-rank agent badge from the DMTC. As he digs deeper into the manor's secrets, he uncovers the horrifying truth—this is no mansion, but a crumbling prison built on the souls of fourteen ancestral guardians, barely containing thousands of calamities. And he has been chosen as the sole heir to inherit their power and end a century-long nightmare.