When William was close to killing the fourth worm, he heard a loud chirp in the air, something that came abruptly, made the hair on his back stand.
"The birds… Damn! What a timing!" William didn't hesitate; the moment he recognised the incoming danger, he instantly stopped all the fighting and retreated.
"Retreat, fast! The birds are coming! Activate the traps at once!"
William instantly shouted, forcing everyone around to disengage and start doing the same: retreat.
To activate the traps they prepared for the thunderous birds, they needed to get behind the defensive dome. Once inside, the different masters started to activate the traps, even before the birds would arrive.
William already explained this beforehand. If they waited to see the birds, they would end up long dead before they would sniff a glimpse of the monsters.
