Beyond the circles of the mortal world lies an expanse of infinite possibility. The Astral Sea is a great silvery void in which countless fragments of divine or mortal purpose drift—dreams, ideas, and wishes, as well as fears and dark desires. All these thoughts and feelings become real and physical in this place. Most are virtually unnoticeable, of course. An ordinary mortal’s passing fancy vanishes in the Astral Sea like a single raindrop falling into a mighty ocean. But dreams and dreads with power are a different matter. The desires of deities or beliefs shared by thousands of mortals take shape as vast kingdoms or even whole worlds within the Astral Sea.
These kingdoms and worlds are the astral dominions—planes adrift within the fundamental expanse of the Astral Sea. Some are heavenly realms of peace and splendor. Some are fantastic dreamscapes filled with marvels and strange perils. And some are dark and tormented places, hellish domains filled with unspeakable evil. Of all the planes, with the exception of the Far Realm, the dominions of the Astral Sea are the most remote from the mortal world. Only the mightiest of heroes venture here.