The Cloud Kingdoms are a land of giants. They exist simultaneously in a dimension of their own and in the sky of every world. One can only enter the Cloud Kingdoms by climbing a magical beanstalk. Exiting is as simple as climbing down a beanstalk or parachuting out of the clouds.
Everyone in the Cloud Kingdoms seems to live in their own castle. There is one High King that rules over the rest of the giants, but it's passed between them often since no one wants the extra responsibilities. The giants of the Cloud Kingdoms aren't very intelligent. Their medicine is medieval and at least one of the giants is proud of being illiterate.
Due to the relative isolation of the Cloud Kingdoms, it is untouched by the Adversary as the Empire has yet to find a feasible means to enter the land of giants, making it one of the few free European fable kingdoms safe from its grasp.
In more recent times, the Cloud Kingdoms have become friendly with Fabletown due to Cinderella's efforts. She managed to get them to allow Bigby Wolf to start a mission to attack the Empire from their kingdom. Eventually, she managed to get them to enter an alliance with them.