These three people were Golden Core Realm powerhouses stationed in Celestial Mist Immortal City.
They were the City Lord of Celestial Mist Immortal City, Jinggu Jade, the Nine-star Daoist Palace Master, Situ Zhengning, and another, who was a Golden Core Realm powerhouse sent by Celestial Mist Sect to guard this place, Yu Wen.
The three each controlled a portion of the protective grand array of Celestial Mist Immortal City, having a clear perception of any unusual occurrences within the city.
Thus, even though Bai Ziyue's attack was hindered by the array without any leakage, it was sensed by them at the first instance.
"That direction seems to be the Celestial Mist Pavilion, Immortal Grade Cultivation Courtyard, Dream Immortal Residence."
"Is someone inside attacking the array?
This strike actually weakened the Tri-Element and Six Harmonies Grand Array of Celestial Mist Pavilion by seventy percent."
