Xi He has always been helping Ye Fan solve problems with ancient cultivators and immortals.
Xi He took a very short time to deal with Emperor Jun, Shun, and several other ancient cultivators who posed a significant threat to Ye Fan, imprisoning them. Then, following Ye Fan's orders, she went to resolve the issues with the immortals. Although these people might not threaten Ye Fan directly, they could potentially impact the safety of Ye Fan and those around him.
After the celestial tribulations, the immortals suffered heavy casualties and had to retreat to a corner of the immortal realm, hoping to rely on the isolation of the immortal realm and the array they formed to block the harm of the celestial tribulations.
When Xi He appeared before these people, they felt a sense of mournful doom approaching.
