It's nothing more than the Koiyuan Tribulation.
What's there to see?
Chou Tian felt like laughing at these words; it was an insult to himself, so he lifted his foot to move on.
However, just as he lifted his right foot, he felt that the space-time he was in seemed to change instantly to a new one...
"What's going on..."
Raising his head in confusion, Chou Tian felt bewildered.
He had not only seen countless Koiyuan Tribulations but had also personally summoned one.
"The Dao Spring is complete, the rules merge, the tribulation arises from peering into the origin, evolves into the Dao Spring, transforms into the Immortal Platform..."
This is the transformation from the Realm of Enlightenment to the Realm of Peering into the Origin, fully explained in less than twenty words.
And the two words "Peering into the Origin" in those nineteen are the qualitative change of the Realm of Enlightenment and the beginning of the Koiyuan Tribulation.
