When Fang Yuan had originally chosen the Charge Gu and Straight Strike Gu as his movement Gu worms, he had already taken the situation at Rank Four into account.
The Charge Gu and Straight Strike Gu were the two main ingredients used to refine the Rampant Gu.
Using these two Rank Three Gu worms as the core, supplemented by the Gu Master's own Primeval Essence and some auxiliary materials, the Rampant Gu could be successfully refined.
Chapter 345