When Zhui Zi was retrieving the Centipede Grass earlier and Wen Leyang when he went to Black and White Island, they once made contact with the descendants of the moon's cone nail. The three siblings - Full Moon, First and Last Quarter Moon, did not jump to fight desperately with them the moment they met. Their attitudes were not considered friendly, but they were not considered hostile either - it was a very awkward interaction. They met twice, and not only were they not involved in the battle of life and death, they even saved Wen Leyang and Zhui Zi on the Black and White Island.
It was not the same this time. When the three descendants of moon's cone nail appeared, the exit of the place of the outer fringe suddenly rippled with Heavenly Moon's top supernatural powers. It was so silvery and bright, just like the radiance of the moon's glow, that it was capable of urging and seizing the soul!
