In an imaginary historical dynasty, the protagonist Li Canghai is a demoted useless prince who is struggling in the struggle for imperial power. He accidentally entered an abandoned ancient book pavilion, touched a mysterious stone tablet, and gained the ability to summon "historical echoes". These echoes are the fragments left in the long river of time by departed heroes, wise men, tyrants and even mythical creatures. They possess great power, but often carry incomplete will and obsession. Li Canghai needs to "locate" and "summon" the "echo" of a historical figure by studying ancient books, inscriptions or relics, and by completing the "obsession mission" or "completing the fragments" of the echo, he can fully exert its power, and even let the echo temporarily "possess" him. But every time he is summoned or possessed, Li Canghai will be affected by the strong emotions that echo, and he may even risk losing himself.
