The two late Nascent Soul stage Great Cultivators had such drastic changes in expression because Qin Fengming had truly given them both a tremendous shock.
For a Foundation Establishment Realm cultivator to refine a high-grade talisman was something even Venerable Dao Ling, who was deeply versed in the art of talisman-making, had never imagined.
At the beginning, Venerable Dao Ling had handed Qin Fengming the two high-grade talismans only to let him gain a better understanding of refining high-grade talismans and become somewhat familiar with them. It would be best if he could gain some experience from the process.
To successfully refine these two high-grade talismans, Qin Fengming would have to wait until he entered the Core Formation realm before there was any chance of success. Even Venerable Dao Ling himself had already reached the mid Core Formation stage when he first succeeded in refining these two high-grade talismans.
Venerable Dao Ling knew very well that the spiritual power and divine sense required to refine this high-grade talisman were simply beyond what a Foundation Establishment cultivator could bear. It was possible that halfway through the refinement, a Foundation Establishment cultivator's spiritual power and divine sense would be completely drained.
With the slightest misstep, being devoured by the backlash of the talisman was also highly possible.
Venerable Dao Ling still remembered clearly what it had been like when he first attempted the refinement. Each attempt consumed nearly one-fifth of his spiritual power. After three consecutive attempts, he had no choice but to stop and recover his spiritual power. If he had forcibly continued refining, he would very likely have suffered the talisman's backlash.
Although refining high-grade talismans carried so many dangers, Venerable Dao Ling still encouraged his disciple to study them. This was something he had only decided after careful deliberation.