Tianji Monument: It is actually a super-time and space artifact made by the ruthless emperor to resurrect his brother "Su Yu" and combine his obsession (seven emotions) with his own Tao Fruit. What it records is not martial arts, but all the "difficult thoughts" and "unfulfilled wishes" in the world.
The truth about the restart of the era: The remnant soul of Su Yu (brother) destroyed the monument because he did not want to be "arranged to be resurrected", causing the countless "obsessions" and "regretful fates" it carried to explode, causing the worlds of gold, ancient, yellow, Liang, Wen and others to collide and merge into the "Nine Realms". The world restarts and all grudges are reset, which actually gives all characters a chance to "re-choose".
