In the alchemy hall.
The Shanliangde Sect elders were about to finish discussing the effects of the Age Regressing Magic Pill and Energy Suppressing Magic Pill. Since both magic pills have no side effects (negative) as Cheng Sheng said, and they trust Cheng Sheng's words, then they all suddenly felt more confident to buy and then use these magic pills. They also have seen the performance of Fei Yin who returned to his youth after eating the Age Regressing Magic Pill as to demonstrate to them its effects.
If Fei Yin, who has returned to his youth after eating the Age Regressing Magic Pill, is already that strong after eating the Energy Suppressing Magic Pill, too, then how much more would it be if Fei Yin didn't eat the Energy suppressing Pill which suppressed his cultivation level?! Coupled with youth, all of them definitely would be very strong!