Kapitel 143: "The Death of An Yue's Parents" 

Because heaven hated cultivators, every cultivator who wanted to ascend to the next realm would have to withstand a heavenly tribulation. 

Heavenly tribulation itself meant heaven would strike a powerful thunderbolt at the cultivator who wanted to ascend. 

If the cultivator was powerful enough to withstand the thunderbolt's strike, they would ascend to the next realm and strengthen their power until they finally became immortal. 

If cultivators couldn't withstand the thunder attack, they would die. 

And this is what happened to An Yue's parents. 

One day, An Yue's parents and An Yue went on vacation to one of the mountains there. 

Because her parents were powerful cultivators, they received enlightenment that told them to ascend to the next realm— the realm above the nascent soul realm. 

If converted to number, the nascent soul realm was already the fourth realm out of the five big realms before becoming an immortal.