Midnight, at the Crystal Pavillion, Quinlan was lying down, staring at the transparent ceiling and looking at the faint glow of stars seeping through. He was frowning in deep thought.
"War..." he whispered for the nth time.
Recalling what happened earlier, he couldn't help but feel pressured. "A war with the alliance."
Right. He was misled by the system into thinking it would be the Demonic Sects that would come and attack. Instead, it was actually the alliance of top sects that was planning to invade them.
In the first place, "Sect Alliance" was already mentioned in the quest itself! There's practically no reason to get confused with it, if not for the sudden side quest about hunting down Yan Yan popping up.
When the quest was updated after Lady Moon's speech, he was finally sure that the enemy this time was the Sect Alliance and not the Demonic Sects.