As the Pandarens managed to defeat the very first Brood Rat Mother through the WARE event, they were elated to see a new teleport portal emerging right above them. Knowing that reinforcements would emerge from it to aid them against those Rat Zurgs, they quickly form a defensive circle around the portal.
They were sure that the minions that emerged from the portal would not backstab them as well as giving them some breathing space to appear out of the portal. But what they did not expect was that they heard a monster sound that was similar to the Rat Zurgs when behind them.
Only a few of the cultivators can spare the effort to look back, causing them to be alarmed momentarily. And the shock eventually spread to the entire defensive circle when the allied monsters did act as the cultivators thought they would. Maybe the mastermind might have appreciated the gesture but her underlings were too eager for a fight.