In the Cultivation World, as long as you remember a cultivator's aura, you can identify them, which is even more effective than remembering their appearance, but that is only possible if there's a chance of meeting again.
And in the Cultivation World, the chance of meeting again is not high. Duan Zhang is a Great Cultivator, and his usual actions revolve around tasks for the Yuqing Sect, with little interaction with other cultivators.
He did not know that when Li Shiming killed Wang Yuan, he did not have his current combat power. At that time, Li Shiming was just a Nascent Soul Early Stage Practitioner, and killing Wang Yuan was merely taking advantage.
The reason why Li Shiming's 'Dark Thunder' spell was so powerful this time, even to the extent of affecting Great Cultivators, was because when he cast the 'Dark Thunder' spell, he used the 'Heavenly Strike Thunder Hammer' and the 'Shenxiao Thunder Pearl.'
