There is only one possibility for this sudden change: Moyang had likely been dragged into the Heavenly Punishment along with the donkey, forced to undergo the tribulation together. Otherwise, two separate tribulations could never have appeared at the same time.
The newly emerged lightning and the overwhelming aura rushing down from the sky were far more intense than before. If lightning of such magnitude were to strike the stubborn donkey, it would probably be blasted into flying ash in just a few strikes.
Not to mention the donkey, even the Saint Clan woman felt that she would not be able to withstand it if she were in its place.
Chapter 709