The Invisible Robeast

S1, E26: Princes Allura and the Voltron Force are out picking fruit, when they are ambushed by an invisible enemy! Allura is taken away, but Pidge manages to free her with his laser blaster and some quick thinking. Shaken up, the Princess stays behind while the others head out in their lions to find the invisible monster. But it shows up at the Castle of Lions and tries to destroy the Blue Lion as it sleeps in the moat. Now, the Princess is the only one who can fight it!