Because Chen Nan and the Divine Calculator took the Soul Destruction Sand from the Array Eye under the Ancient Altar Array, causing the Great Array sealing the Demon Clan to loosen.
The Demon Ancestor regained some strength and captured many cultivators, placing restrictions on them, forcing them to go and destroy other Ancient Altar Arrays.
On one hand, it was due to the pressure of the restrictions; on the other hand, destroying the arrays could yield Heavenly and Earthly Treasures from the Array Eyes.
Thus, even with the Corpse Puppets guarding, the cultivators continue to forge ahead, like moths to a flame, toward the ancient altars.
The news that the ancient altars held Heavenly and Earthly Treasures quickly spread, causing more and more cultivators to flood into the Southern Marsh, creating a treasure hunt frenzy.
Killing and looting became the norm.
