The Heaven-and-Earth Calamity arose because of humanity.
Fundamentally, the path of Longevity Realm pursued by cultivators was one of stealing from Heaven and deceiving Earth, of mortals and Heaven battling one another, ultimately overcoming Heaven and Earth by a thread and defying fate to alter one's destiny.
In this process, if humanity won, they would rise above through Transcendence; if humanity lost, they would be crushed beneath the wheels of heavenly fate.
As days and months accumulated, traces would inevitably emerge within the originally complete and orderly system of Heaven-and-Earth laws.
Once those traces accumulated to a certain degree, it was like a spring compressed to its very limit. It would naturally trigger a "repair" by the laws of Heaven and Earth, and to cultivators devoted to battling Heaven in pursuit of Transcendence, that "repair" was a tribulation blocking their path.
This was the Heaven-and-Earth Calamity.
Every Heaven-and-Earth Calamity was a critical moment when the Nine Heavenly Human Arts were constantly stirred, and also the time when the great power of Heaven and Earth was at its strongest.
The more profound a cultivator's cultivation, the more they had to "avoid the tribulation" at such times, because they were precisely the targets of the Heaven-and-Earth Calamity.
Of course, it was also an opportunity for exceptional talents to rise. A small tribulation brought small divine abilities; a great tribulation brought great Creation.
Braving the difficulties amid a Heaven-and-Earth Calamity and directly facing the immense power of Heaven and Earth as the Nine Arts shifted was the opportunity to attain the highest fruits of achievement.
Naturally, many factions would also seize such opportunities to stir up storms and rain.
During the last Heaven-and-Earth Calamity, the Western Heaven Buddha Realm rose with the tide. Though its missionary efforts in the Central Land ended in