According to the prophecy, the Holy Ancestor shall return and the cycle shall restart.
What's prophesied before has come true, so the rest is likely to be accurate as well.
Since Purple Lightning has already met Lin Yun, how could he doubt Qing Shuang's statement?
Could it really be that someone does not believe in the ancient prophecy?
Therefore, it is entirely possible that Demon Venerable You Lan and Red Silk Demon Venerable choose to seek peace at this time, since they have not yet been able to successfully seize the bloodline of the Demon Emperor.
"Since they are willing, then I shall attend tonight's banquet."
Seeking peaceful resolution, Purple Lightning also does not wish to conflict with the other two Demon Venerables.
Having gained the favor of the Demon Ancestor, her stature is no longer merely at the level of a Demon Venerable.