After the ancient war between immortals and demons, the mythical beasts from the Classic of Mountains and Seas were not truly wiped out. Their physical bodies disintegrated, while their souls took the form of "artifact spirits," inhabiting objects in the mortal world and sleeping for a thousand years. Some people are born with a special constitution and are known as "Spirit Collectors." They can sense artifact spirits, awaken them, and form contracts with them. Once an artifact spirit recognizes its master, it can take physical form from its vessel and fight alongside its collector.
