The name of this article wasn't revealed in the novel and instead was given by editors of the wiki as substitute for lack thereof.
30,000 years ago, Black Dragon King suddenly attacked Immortal Emperor Ta Kong for unknown reason. After that battle Black Dragon King and Immortal Emperor Ta Kong disappeared, while the Heaven's Will was torn apart.
This battle ended the Emperors Era and heralded the start of the Difficult Dao Era. Without the Heaven's Will, the Nine Worlds' energy dried up and this became the hardest 30,000 years for cultivators.