Avenge the village. Avenge little sister Rou. Burn. That. Sect. To the ground.
@gherig and @Siikalahna
Go back and read the last chapter. One of the head sect disciples told an underling to go get the Formation Breaking Cartridge. That was the device that the sect leader warned him they had to break any formation. While he was eating dinner with the sect leader that other guy obviously sent some people to go break the formation and kill his people.