The Daylight Sky Immortal Secret is the Heaven's Will Secret Law created by Immortal Emperor Min Ren.
Min Ren had left behind his Secret Law to the Cleansing Incense Ancient Sect; unfortunately, the Sect lost it later on.
At some point, before it was lost, experts from the Cleansing Incense Ancient Sect derived a Minor Emperor Merit Law from the Daylight Sky Immortal Secret, the Daylight Sky Merit Law.
Li Qiye regained his memories about the Daylight Sky Immortal Secret after studying the Daylight Sky Merit Law and brought its complete manual to the Cleansing Incense Ancient Sect. However, it become the top secret of the Sect. Besides Li Qiye, only the five elders knew about it.
After entering the Evil Infested Ridge, Li Qiye used Daylight Sky Immortal Secret to deal with Sinister Bird Plant.
Daylight Sky Immortal Secret allows to emit a blinding brilliance and control all light in the world. It looks like a blue sky surrounded one with sun, moon and stars hovering around.
Links 3 Appearance(s) of Daylight Sky Immortal Secret