A powerful crystal in the care of Wren, leader of the resistance movement on Terra Gale. This stone can produce staggering gusts of wind, powerful enough and controlled enough that they can be used to hurl large objects long distances. Wren gives the Stone to the Storm Hawks after they save his granddaughter, Dove. The crystal was supposedly destroyed in the episode "The Last Stand" when Radarr was trying to cool down the engine with the wind that it created. However, it is possible that Piper gave Radarr a different Windstone Crystal.
The Windstone Crystal is green, with two flat sides outline shape vaguely like an egg with points.