From the very beginning of Shen Feng's battles with the World Beast swarms on Earth, he had been continuously wounding them. Every single cannon shell and Kinetic Energy Bullet was already packed with Nanomechanical Clusters.
Even every slice of his Battle Blade left Nanomechanical Clusters behind in the World Beasts' wounds, which ceaselessly devoured the behemoths' flesh and spread throughout their entire bodies via their circulatory systems.
At first, this corrosion was slow and insidious. The nanites attacked the nervous system first, completely destroying it before the World Beasts could even feel any pain.
From that foundation, they began to corrode and devour them bit by bit.
Due to the strong electromagnetic environment within the World Beasts' bodies, this process took a very long time, continuing until the number of Nanomechanical Insects surpassed a certain critical point.
This was why Shen Feng had waited until now to fully summon the Gray Tide.
