The Sky Siren is an illusion-casting witch intent on destroying anyone who enters the Great Expanse. She uses their greatest desires against them, keeping them from escaping. Her illusions manifest themselves in the form of what appear to be waking dreams. Many ships and people fell prey to her power until the Storm Hawks. One by one the Storm Hawks fall prey to her powers, but in the end it is Radarr who overcomes her and pilots the ship to safety, the act of doing so having been his greatest desire, driving the condor. Which shows to break the spell of the siren, the greatest desire must be seen. Episode 23 "Siren's Song".