Let's just call it a chain.
This so-called "chain" was actually a taboo art, one that deceived the Celestial Dao and stole destiny.
The essence of the Grotto Heaven Grafting technique was to use a Secret Technique to deceive the Celestial Dao, forcefully stealing the Root Origin Qi of a Small Thousand World and grafting it onto one's own Dao Foundation.
This technique was exceptionally dangerous. The slightest misstep would trigger a backlash from the World Heaven, with consequences ranging from the destruction of one's Dao Foundation to the complete annihilation of one's Divine Soul.
However, success was akin to plundering creation itself, claiming a world's Power of Origin as one's own to form a Grotto Heaven Embryo.
