In the late Eastern Han Dynasty, he became an inconspicuous registrar under Cao Cao. While others assisted their lord with utter devotion, he assisted his lord by stopping him from seeking death every day; the lord was rushing to be reincarnated, and the first thing upon transmigrating was to persuade the lord to live a couple more days. Relying on the Three Kingdoms history memorized back and forth, Li Yuan made a great splash in Cao's camp: conducting entrapment to root out corruption, mixing sand into porridge to manage refugees, trading three carts of leftover grain for a mountain stronghold, intercepting Dian Wei at the alliance meeting, slaying Hua Xiong in three rounds, and even stealing the traffic of Zhang Fei's legendary roar at Changban Slope.