It took two days for Mu Chen to completely condense the Pseudo Spirit of Fighting Intent for the other three armies. After completing the task, he was left feeling utterly weak for an entire day.
Refining the Spirit of Fighting Intent was not only draining in regards to one's spiritual energy, but it also took a toll on one's willpower. To control the will of tens of thousands of people required a high degree of willpower. This was one of the main reasons why many strong and powerful men are still unable to control the will of fighting intent.
Continuously condensing the Spirit of Fighting Intent for four armies, and finally sealing the imprint in the minds of all the soldiers, was no easy task. Hence, when Mu Chen was done, he was very fatigued, only gradually recovering the next day.