The false dragon was a flying spirit and the only one that Winged Skull had actually went all the way to specifically create. It was huge and the Winged Skull had even added a purple-gold sack in the false dragon's mouth, capable of carrying large amounts of toxin essence. When the essence was added to the poisonous mist that the false dragon breathed, it enabled the beast to continue spewing for over an hour.
No other flying spirits had such powers, but having 30 to 50 of them attacking a small camp would yield similar results.