Open Sky was the collective term for the uncharted sky far above and around the Edge cliff. Open Sky was universally feared by all inhabitants of the Edge, as both terrible monsters and deadly weather patterns existed there. It also had religious and spiritual meaning to inhabitants of the Edge, and it was commonly believed that the spirits of the deceased floated up into Open Sky. Open Sky seemed to extend forever upwards and to the sides as no one had dared try and find the boundary thanks to the above perils and the stigma of superstitions attached to it. Additionally, the Mother Storm resided in Open Sky, and every five or six thousand years, it returned to the Edge to rejuvenate the Edgewater River. Open Sky was also where the sun, the moon and stars and constellations like Borius or Mitras were located.
During the events of The Winter Knights, Quint and his friends flew the sky ship Cloudslayer out into Open Sky in order to heal a cloudeater whose illness caused an unseasonable winter in Sanctaphrax. Later, during the events of Midnight Over Sanctaphrax Twig flew the vessel Edgedancer into Open Sky to find his missing father, Cloud Wolf.