The disciples of the Black Lake Sect had been quite worried. These disciples were the ones who were stationed to attack the barrier that the Night Mountain Sect had set up. According to the formation, they were the wings who were to attack the Night Mountain Sect.
Basically, they had to lure the Night Mountain Sect's cultivators. Once these cultivators would come out, the other warriors of the Black Lake Sect would reveal themselves and attack them.
This would be a surprise attack that would completely catch them off-guard. Naturally, even though this attack had come out of Erica's mouth, it was actually an order from Azaroth.
By doing this, he was giving the Night Mountain Sect a chance to gather their forces. In reality, the simplest method to end this entire battle would be to have all forces of the Black Lake Sect advance when the Night Mountain Sect's barrier was down.
