Tang Shaoyang felt so exhausted even though he did not do anything related to physical activity. However, he felt so exhausted addressing the issue of his affair with Ava. After taking the oath and securing the Elven Kingdom's loyalty, he had to explain everything to Wei Xi and the others. Everything included the oath he took in front of the three siblings.
Tang Shaoyang took this seriously because he might lose his subordinate's trust, especially for his subordinate with a wife. He did not want them to fear that their wives would be taken by him. That was not something he wanted to happen, so he assured them what would happen to him if he broke the oath.
If he broke the oath, then he would have to abdicate his position and leave Earth. If he did not do so, then death was his next punishment. That was an assurance, not just for Virion, but for Wei Xi and the others too. He put his status as emperor, even his life, on the line.
