If malicious thought Gu were used to replace delight in water and mountain Immortal Gu, the quantity of the former would definitely have to be enormous.
Fang Yuan needed a lot of malicious thought Gu and not just several hundreds of them. He made an initial estimation that he required at least two thousand, by simultaneously activating them, the amount of malicious thoughts they produced could barely be sufficient for use under the light of wisdom.
Most importantly, these two thousand malicious thought Gu must be rank five.
Fang Yuan had the recipes of rank one to rank five malicious thought Gu. Rank one to rank five malicious thought Gu had similar effects in producing malicious thoughts. The only differences were the amount of thoughts they could produce in one activation and the vast difference in the quantity of primeval essence they consumed.