Seeing so many powerful and highly concentrated heavenly thunder, the Kings of Hells were dumbfounded.
This was because the intensity of the Heavenly Tribulation was not the intensity of an ordinary Nascent Soul Stage tribulation.
If every Nascent Soul Stage tribulation is at this level, then it could be said that there would be no Nascent Soul Stage out of ten Core Formation Stage cultivators or maybe not even one in ten thousand,
And as the Heavenly Tribulation increased, the black tortoise array formation set up by Lu Yuan also began to shake, as if it would break at any time.
The Kings of Hell felt that once Lu Yuan's array was shattered by the heavenly thunder, it would be almost impossible for him to survive the Heavenly Tribulation even if he had amazing talent.
But gradually, the expressions of the Kings of Hell changed from worry to confusion.