Kapitel 377: Loud Thunder, Drizzling Rain

The reason Zhang Lisheng could create the Gu Sea Method was because, first, among the spells he had obtained before transformation, he had the two spells of 'assemble'—that allowed him to search and refine wizard gus with a speed that was a thousand times faster than an ordinary wizard, provided that he did not carry out a fine selection—and 'refine', that allowed him to turn something evil into something pure easily by turning those weak wizard gus that they did not carefully select to become strong and fierce. 

Second, it was because, after he had become a wizard, he had once sealed the ancient strange worm statue into his body before; thus, it allowed him to command the wizard gu by just solely relying on the strength of his wizard gu, regardless of his own mental strength.