First, it was to control and master the changes to the spirit designs of 10,000 Immortals Palace. 

Activating, manipulating, transforming. 

Through the Yan Huang Dragon Insignia, everything was within his control. 

This was another application of the spirit designs. First, the cores of spirit designs were laid on an elite dao treasure. After which, one could control the Heaven and Earth Spirit Design through the dao treasure. 

There were lots of spirit designs in 10,000 Immortals Palace, layer after layer. Perhaps it was because they were used to protect the treasury. Therefore, they had to be rather impenetrable. For any intruders, they would be their nightmares. 

Obviously, they also served to protect the emperor and the royal consorts. After all, this concerned the lineage of Yan Huang. Many princes and princesses were raised in 10,000 Immortals Palace. It was only when they had reached teenage years that they would move out of 10,000 Immortals Palace and receive their own prince or princess' residence. 

Wu Yu gave it a try. Within 10,000 Immortals Palace, the activating, shutting off, and changes in intensity of spirit designs were all under his control. He could even control who could enter or exit. Together...