Lin Chen, an outer sect disciple of the Xuantie Sect, is born with a "dull meridian" that prevents him from activating magical artifacts. He is publicly humiliated by Zhao Wuji, the top inner sect disciple, and falls into the sword-forging pool. At the brink of death, ancient inscriptions suddenly emerge on the heavy, edgeless ruler strapped to his back: "As long as the heart's flame never dies, dull iron can shatter the heavens." From then on, he enters the Heart-Refining Formation and devours its core, then awakens countless lingering souls in the Tomb of Ten Thousand Weapons by embracing rather than striking. Along the way, Su Mo, a genius of the outer sect, makes a pact with him using a red thread and remains by his side. Zhao Wuji, once his sworn enemy, comes to his senses on a snowy slope in the frozen wasteland after the furnace is destroyed and he loses his mind. The three journey through icy tides, brave spirit towers, and traverse the Eastern Wilderness, Western Seas, and Southern Mountains, ultimately discovering the ultimate meaning of the six techniques of the Heart Transmission.