Elemental Plane

The Elemental Plane is a pocket dimension created by the Keepers to imprison Azeroth's elementals. The prison plane consists of four interlinked domains, each representing one of the major elements - Skywall (air), Deepholm (earth), the Abyssal Maw (water) and the Firelands (fire). Highlord Demitrian described it as "the core of this world".

Creation
Azeroth's native elementals wreaked havoc across the world while they served as the lieutenants of the Old Gods. After defeating them, the titan-forged chose not to destroy the elementals, since they were bound to Azeroth and would manifest again. Instead, the titan-forged chose to imprison them in a pocket dimension. Four domains were created within this primordial realm to serve as ideal environments for each type of elemental - The Skywall (air), Deepholm (earth), The Abyssal Maw (water) and The Firelands (fire). Highkeeper Ra, one of the Keepers, and Helya, a titan-forged, created the Plane for the titans and used The Highkeeper's Ward to seal off the Elemental Plane from Azeroth. For ages since, the elementals of air, water, earth, and fire have engaged in endless strife with each other, waging titanic battles in the confines of their realm. The greatest of their battles was the Elemental Sundering. With the elementals' departure, nature calmed, and the world settled into a peaceful harmony.

Aftermath
Ragnaros the Firelord once commanded the Fire domain in the plane, but 300 years ago Dark Iron dwarves in the Redridge Mountains summoned him to battle their enemies. The catastrophic summoning blasted the land and immolated the Dark Irons, and Ragnaros sunk into the depths of Blackrock Spire to prepare his return.

World of Warcraft
Recently the elementals have learned to open portals to start Elemental Invasions. At the beginning of an elemental invasion, portals will open to the elemental planes and invaders will begin to pass through. Thus, during an invasion you will find two to three times as many elementals in the area, usually slightly higher in level than the standard ones found there.

World of Warcraft: Cataclysm
Shortly before the Cataclysm Elemental Rifts spawned in nearly every zone on Azeroth. Following Deathwing's Shattering of the World Pillar in Deepholm and his destructive re-emergence into Azeroth, the Elemental Plane collided with the physical realm and resulted in drastic geographical upheaval, causing chaotic elementals to pour out into the world of Azeroth. The boundary between the mortal planes and the elemental plane was severely damaged and the elemental planes can now be reached through various means by the heroes of Azeroth.
 * The Skywall is reachable from Uldum and hosts the Vortex Pinnacle 5-man dungeon and the Throne of the Four Winds raid.
 * The Abyssal Maw is accessible from Vashj'ir and hosts the Throne of the Tides 5-man dungeon.
 * Deepholm is a full-fledged zone tuned for level 83 players. It is accessible from a portal at the Eastern Earthshrine and Western Earthshrine. Deepholm hosts the Stonecore 5-man dungeon and is the home of the Therazane faction and its associated daily quests.
 * The Firelands appear in bits and pieces in Mount Hyjal quests and as a full-fledged zone Molten Front with daily quests and a raid.

Some time after Al'Akir's death, when Typhinius obtained the Fists of the Heavens and returned to the Skywall, he immediately set out to end the air elementals' civil war. He flung the spirits of those who had opposed him into the other elemental realms. Alone, they could not stop their natural enemies from finishing them off in a slow and agonizing fashion.

In the RPG
During the several millennia, the elementals grew attached to their adopted home. Then, the summoners of Quel'thalas and the human magocracy learned to command the elementals, inadvertently opening momentary pinholes between Azeroth and the Elemental Plane. Elementals are sometimes called back to Azeroth for short periods of time, but most are eager to return to their world when the spell that summoned them ends.

Geography
The Elemental Plane is described as "a prison plane in the Twisting Nether". The Elemental Plane was fashioned by the titans as a separate plane within the Twisting Nether to hold their old foes. The plane the titans created is spherical and comparatively small — about the size of a single world. It is a three-tiered realm. The domain of Air sits atop the middle layer, which supports both the Water and Earth domains. Beneath these lies a third layer of Fire and molten rock.

The sphere of the plane itself is curved in a curious way that tends to baffle creatures of Azeroth's reality. As befits the plane's prison function, escaping through ordinary movement is impossible. A creature attempting to move out of the sphere simply curves inexorably around, moving toward the other side. Thus, if one were to sail across the ocean in a boat, he would eventually arrive on the exact opposite side of the plane's sole continent. The land itself is slightly larger than Kalimdor, while the seas are about the same width in all directions. The continent is known as Deephome.

Khadgar appears to agree with Highlord Demitrian as he thinks that "atop of the Elemental Plane sat the mortal, material worlds". It would look like any other world to an outsider — at least, when looked upon from above or on the ground: one large continent surrounded by water, with a yellow sun burning above. A casual visitor, arriving on the surface, might even believe he is on an ordinary — if somewhat violent — planet. A glowing yellow orb, casting forth light and heat, hovers near the top point of the globe, acting as the "sun" for the entire plane.

Traits
Communicating with elementals is difficult, and they have provided little information about the nature of their realm. But it is known, that lava flows, earthquakes, windstorms, and tsunami are common, making the Elemental Plane a very dangerous place to visit. Normal levels of gravity pull physical objects toward the bottom of the sphere, where the realm of fire lies. The four elements that make up the plane are constantly in opposition and tend to shift and tear at each other, sometimes violently. Volcanoes rip through the solid mantle, assaulting both the land and sea realms wherever they can. The air swirls in unpredictable storms, producing whirlwinds and hurricanes that rake the surface. The elemental beings can alter the plane with a thought. The landscape shifts on its own from time to time. Spells and spell-like abilities with the air, earth, fire and/or water descriptor are empowered and enlarged in all regions of the Elemental Plane.

Azeroth's denizens have few dealings with the Elemental Plane, though they can access it with magic. It can also be accessed with "transit nodes", which are specific locations in Azeroth that connect with the Elemental Plane; these transit nodes exist only in specific elemental-based locations, such as within a volcano, underneath deep oceans or lakes, and the like.

Creatures
Each of the realms is filled with life of various types, although the Abyssal Maw is mostly populated by elementals. The native creatures are just as dangerous, as the world plays home to angry elemental creatures of all types. A few natural animals can also be found, including some creatures never seen on Azeroth. These creatures have adapted to survive in the environment, and the Elemental Lords take special care to protect them. The basic elemental types can be found in the plane, and there are examples of elemental conglomerates as well.

Trivia

 * The Elemental Plane was originally said to have been constructed by the titans after they defeated the Old Gods.