The Elemental Realm is a realm within the Veil. It is comprised of a number of discrete, massive spheres, each made up of a vast quantity of a single element. Most of these spheres are incredibly inhospitable to an unprotected traveler.
The Elemental Realm can be reached via teleportation ritual using the numerological key of 4. Elementals are commonly summoned by mages, and are considered a relatively safe summon, since they are simple beings lacking complex thought, and easily controlled.