Reborn as a Snake: Many Children, Many Blessings, Only I, the Green Snake Immortal

In a world ravaged by demons, Xu Qing transmigrates and becomes a green snake in the Hundred Thousand Mountains.
The mountains are fraught with danger, and monsters roam freely. To survive, one must increase one's strength.
Fortunately, Xu Qing is now bound to the "Many Children, Many Blessings" system, and can receive rewards for having offspring!
"Your descendants exhibit ancestral atavism, and you gain supernatural powers—the ability to control the wind and rain!"
"Your descendant has advanced to the Refining Spirit Realm, and you have gained five thousand years of cultivation!"
"Your descendants have surpassed one hundred million; you have attained the rank of True Immortal!"
When the human world fell into chaos, and the gods descended to cleanse it, they were horrified to discover that a terrifying being was lurking in this world!
That day, Xu Qing awoke with a start, his vertical pupils like a full moon, illuminating the world!
"Who dares to disturb my peaceful cultivation!"