In the end, the old priest agreed because he really owed Long Yu a favor. If he didn't repay it, he would have felt really bad.
"Haiz, worldly matters are just so complicated. Apart from relationships, I am most afraid of favors." The old priest felt really depressed. He hid in the clouds where the breeze and moon circled him.
He didn't want to head down and hang around with those mortals.
....
In the Bank of the Universe, Moon Angel returned back after completing her mission.
"Master, the 10 Dao Saints have all been killed." Moon Angel Usuna said calmly.
"How was it? How was Full Moon?" Li Xiandao asked curiously.
"Very good, this should be the most suitable weapon for me. With it, I can kill those two at the Countless Sands Realm." Moon Angel said confidently.
With a Celestial Artifact in hand, if she didn't have the confidence to do so, Usuna wouldn't be worthy of wielding Full Moon.