Elemental Plane of Earth

The Elemental Plane of Earth was an Inner Plane or Elemental Plane of the Great Wheel cosmology and the World Tree cosmology models. After the Spellplague, the Elemental Plane of Earth collapsed into the Elemental Chaos, mixing with all the other Inner Planes. Earth is one of the four elements and two energies that make up the known universe and therefore of keen interest to cosmologists. The abundance of large gems and huge ore deposits lured many greedy prospectors to brave the significant dangers of this plane.

Cosmology
According to the Great Wheel cosmology model, the Elemental Plane of Earth could be reached via the Ethereal Plane, an adjacent elemental plane, or by an elemental vortex. If traveling through the Deep Ethereal, a brown curtain of vaporous color indicated the boundary of the Plane of Earth's Border Ethereal region. Once in the Border Ethereal, a traveler could observe the Plane of Earth and be detected by its denizens. Using the spherical model, this plane was adjacent to the para-elemental planes of Ooze and Magma and the quasi-elemental planes of Minerals and Dust. Elemental vortices could occur wherever a high concentration or nearly pure form of an element was found, and could be temporary or permanent. Vortices to the Plane of Earth were nearly always found in the heart of mountain ranges, particularly young ones. Temporary gates could be created by the plane shift spell or the abilities of high level druids.

In the World Tree cosmology model, the Astral Plane connected all planes with the Prime Material Plane and the Ethereal Plane was only used for journeying between locations on the Prime. The Elemental Plane of Earth was not connected or coterminous with any other elemental plane. The spell astral projection could be used to reach the Plane of Earth via a moss granite color pool. Additionally, the gate and plane shift spells could be used to open a temporary portal to this plane, but could be extremely dangerous unless the destination was previously scouted.

Description
"It is a place of hidden riches. It is a wall against all foes. It is a grave for the greedy."

- Manual of the Planes

The Elemental Plane of Earth was an infinite expanse of solid matter pockmarked by bubbles of other elements and riddled with fissures and tunnels created by burrowing creatures or the occasional small mining operation. Solid does not imply stationary: the substances of this plane were constantly moving in a slow, grinding motion punctuated by earthquakes from small tremors to massively violent upheavals. Open spaces were gradually filled by the relentless shifting (or marauding earth elementals) unless action was taken to prevent it. Air could be found in scattered pockets but unbreathable gasses were also present&mdash;unprepared travelers lucky enough to arrive in a cavern might slowly asphyxiate while the unlucky quickly suffocated by being buried alive. No light existed in the Plane of Earth except for rare luminous gems buried in the crushing darkness. Travelers able to pass through stone were effectively blind until their ocular organs reached an open space where a source of light could be produced, or they used magic such as a ring of x-ray vision. Hearing was actually enhanced while encased in earth; to the point where a traveler could detect any movement through the rock within a certain radius of her position.

Every type of rock, soil, mineral, metal ore, sand, and dirt could be found here in abundance, ranging from talc soft to marble tough to diamond hard. Mining operations tended to be small and short-lived because the movement of the substance of the plane and intense gravity caused cave-ins, and the native population defended their territory and/or food supply. In addition, there was the unusual problem of where to put the discarded mine tailings. The dao were the only people known to successfully manage large continuous mining operations in the Plane of Earth. They did this in the Great Dismal Delve mercilessly using slave labor to dig and repair earthquake damage.

Inhabitants
The matter of the plane itself come alive, the earth elementals were the most numerous creatures on the plane,  with typically blocky, angular bodies covered in sharp edges, ranging from man-sized to mountainous. Other native creatures looked like rough-hewn statues of Prime Material Plane animals and monsters or animated crystalline forms like crysmals. Then there were the alien-looking khargra, xorn, and xaren with tri-fold symmetric bodies and a taste for metal. All natives and some creatures with an earth-affinity could move through the plane like a fish through water, the rock flowing around them and closing back up again, leaving no tunnel. (See Notes)

Immigrants and visitors to the Elemental Plane of Earth included basilisks (greater), the dao,  dwarves, an occasional blue or copper dragon, gargoyles, janni, lava children, mephits of the earth and salt subtypes, the pech, sandlings, stone giants, thoqqua, and wraiths.

Realms

 * Geb of the Mulhorandi pantheon once had a realm here.
 * Grumbar, the Lord of the Earth, Gnarly One, King of the Land Below the Roots, Boss of Earth Elementals,     was thought to be a mountain-sized earth elemental with greater-god-like powers that rarely granted audiences. After the Spellplague it was revealed that he was a primordial and he formed a new realm called Root Hold in the Elemental Chaos.
 * Ogremoch, Prince of Evil Earth Creatures, once had a citadel atop a large mesa within a huge pocket of vacuum.