I dug through as many old D&D products that I could find to compile all of the material on this plane in one place. When it comes time to use the Plane of Elemental Earth, you can sort through this and pull out the ideas you like.
The Essential Information
- The Plane of Elemental Earth is one of the Inner Planes.
- The Sevenfold Mazework: Earth genies have a vast city/labyrinth known as The Sevenfold Mazework.
- Ogremoch, Evil Elemental Prince of Earth: He lives here on a vast mesa and a plateau made of the dead bodies of his enemies.
- Sunnis, the Good Elemental Princess of Earth: She opposes Ogremoch. She lives in Sandfall, a cave under a perpetually falling column of sand.
- Grumbar the Living Mountain: A massive earth deity who lives here as well.
- Granite Gloom: This locale from Tales of the Outer Planes is a really cool genie lair with geometrically-shaped rooms and a garden of floating crystals.
- Earthsblood: This stuff is from Egg of the Phoenix and is a highly sought-after substance with many magical properties.
- Portals: There are portals to Sigil, Elysium, Hell, the Spine of the World Mountains in the Forgotten Realms and many other elemental planes here.
- Monoliths: Monoliths are basically greater elementals linked to the plane.
- Earth Weirds: These stone women can see into the future.
- Primordials: There are at least 3 primordials trapped here in some fashion.
- The Pillars of Creation: These pillars are each made of different types of rock and may hold up the entire plane.
- Primordial Shards: These are prized magic items that bond with the wielder to give them the power to become an elemental being.
- Races: It seems like earth genasi and maybe goliaths should have a bigger presence in this plane.
In the Dungeon Master's Guide on page 52, the inner planes are described as being enveloped in the elemental chaos. The edges of each elemental plane are more inhabitable and are the domains of elementals, the Elemental Princes and others. It is said that the center of the plane of Elemental Earth is solid earth. Other factoids:
- Opposes the plane of air.
- It is a chain of mountains bigger than any in the material plane.
- The largest cavern is known as the Great Dismal Delve or the Sevenfold Mazework.
- The Furnaces: These mountains are near the plane of Fire. There's a lot of lava and dao forges.
- The Swamp of Oblivion: This is also known as the Plane of Ooze. This is the region where water and earth connect. An object thrown into the swamp can't be found for at least 100 years.
- Every building is made from precious stone and metals.
- The city is guarded by a spell that alerts all of the dao if a single stone is stolen.
- Theivery is punishable by death and might be extended to the relatives as well.
I'm pretty sure you could take most of the earth node/The Black Geode and repurpose it for the Elemental Plane of Earth. It has a few cool things, like the earth mephits spawning.
Now let's go through old editions and see what we can dig up. We'll start with 1st edition and go up from there.
Tales of the Outer Planes
Tales of the Outer Planes is really goofy in parts, but I have to say this area is really cool. You can take all of these things and do cool stuff with them. There's two scenarios. One involves a captured princess, and the other one is a really weird place infused with radiation.
The Missing Kristal: A dao has captured Princess Kristal and taken her to his lair in the Plane of Elemental Earth, Granite Gloom. A wizard uses plane shift to send the group there.
Here's the flavor: "A wide river flows by the alcove entrance, filling the vaulted cavern from wall to wall. The river's surface is flat and as smooth as glass, despite its speed. Swirling eddies of brown, gray and blue can be seen. Shockingly, this river is made of flowing stone!"
The Well of Thunder: The river eventually spills into a hole in the floor. If you fall in, you die "in the maelstrom of breaking rock below."
The Gravel Lake: You can walk on this, if you are careful.
Kristal is trapped in a crystal garden. The group needs two gemstone keys to get in there.
In Granite Gloom, there's a bunch of weird rooms shaped like cubes or pentagons. There's one that is a sphere with walls made of sand. There is a "demi-power" earth elemental named Jaggak, a distant cousin to Grumbar. He's 60 feet tall. I think he's under the sand. The group is meant to fight just his arm..? If the group annoys Jaggak, his head will pop out of the sand and he will demand a magic item. He somehow knows all of their items, and demands one of the three most powerful items.
The Crystal Garden: It is full of floating crystals of all colors. Some are the size of a house.
Several of thee crystals are magical prisons. From the outside, all you can see is a dark shape moving in it. One of the prisoners is Kristal. The others:
- A Marid who was tricked into getting trapped.
- A basilisk
- "13 exotic creatures of the elemental plane of earth"
Failing two saves means that your hair falls out, you're nauseous and you will lose d10 hit points per day until dead or magically cured.
Egg of the Phoenix
Egg of the Phoenix is a gigantic adventure that takes you to the Negative Material Plane and many other places. There are quite a few links to the elemental planes.
To start with, the kingdom has a miracle substance called Earthsblood. It is black, liquid goo and in many ways is portrayed similar to the role of oil in our world. Earthsblood might be the secretion of a great creature living deep in the heart of the earth. It:
- Lights homes
- Powers furnaces
- Provides materials for wizards
- Heals the sick
- Cure baldness!!
- Smells bad
If the group goes in, here is some of the flavor:
"In the midst of the mesa sits a half-formed giant, a blobby mannequin of clay. The thing's soft features turn to face you, hardly aware of your existence. Yet moments later, the earth shakes under your feet, a great crack opens and your point of view drops deep into the fissure."
While Ogremoch is actually civil with the heroes, later in the adventure he sends elementals and xorn to try to steal the Egg of the Phoenix from them.
Dragon Magazine 77 - Elemental Gods
This article details gods from somebody's home campaign. Maybe you can do something cool with it. Really the best part of this article is the author talking about how awesome their campaign is.
The Allmother: Goddess of birth, farming and fertility. She rules all animals. She has an evil aspect which rules plague, poison and decay.
She has many names: Giver of Gifts, Earthshaker, Bearer of Burdens, Mother of Horses, Pourer of Poison, and Mother of Vipers.
Now let's jump into 2nd Edition, which has a lot of awesome stuff.
The Inner Planes
The Inner Planes is a Planescape supplement that gives a real good look at the Elemental Plane of Earth.
Creatures that dwell in the elemental plane of earth: Crysmal, dao, dao noble, earth elem, earth mephit, galeb duhr, sandman, earth genasi, xorn, svirfneblin (deep gnomes), dragons, basilisks, cockatrices, medusae, goliaths, earth genasi, neogi (who enslave umber hulks) and stone giants.
Grumbar: The Living Mountain, Earth Father. God of earth elementals. Those who visit with him come to a vast wall of stone, on which the face of Grumbar appears.
Elemental War: Sunnis, the Good Elemental Princess of Earth and Ogremoch, the Evil Elemental Princess of Earth fight for supremacy and domination. Grumbar sits by and watches.
Portals:There are a number of known portals to the Plane of Elemental Earth:
- There are a few in Sigil.
- Mechanus: The modrons have this giant planet-sized contraption that is somehow powered by continental drift. This machine is an eternal key to elemental earth. It is a one-way portal.
- Hell (Phlegethos, the fourth layer): Ogremoch's citadel, Stonemire, contains a portal to Hell. It leads to an evil fortress called Abriymoch ruled by a pit fiend. Ogremoch is allied with the pit fiend.The key to this portal is a large diamond, which turns to powder when used. There are guards on either side.
- No Air: Some areas have no air.
- Gas Pocket: Explosive, noxious (stinking cloud), or toxic (cloudkill).
- Links: Planes of magma, ooze, mineral and dust.
Fiery Cascade: A stronghold between pockets of elemental fire that has 3 dimensional flaming moats.
Stonemire: Ogremoch's fortress. It has fountains of molten stone, clouds of hot smoke, and geysers of scalding steam. There is a plateau made up of the bodies of his enemies.
Sandfall: Home of Sunnis, Good Elemental Princess of Earth, the Lode Mother. This is a cavern under a perpetually falling column of sand. The sand falls in bottomless pit. It is built around a gleaming crystal 50 feet across. She likes unique treasures.
Secrets of the Lamp
Secrets of the Lamp is one of my favorite Al Qadim supplements. This thing literally details the entire area known as The Great Dismal Delve.
The Great Dismal Delve: Dao have the most hierarchical society of all elemental races other than the efreets. The sharif is the supreme ruler, ensconced in the race's ancestral home in the Elemental Chaos. This place, called the Great Dismal Delve, is carved into a massive block of freestanding earth. Though the dao constantly bore through its interior, the stone constantly renews itself from within so that they can never remove it all. This cycle of activity spawns great earthquakes that rattle through the Delve.
- Tunnels and roads lead to the Sevenfold Mazework
- Full of toiling slaves
- The dao use Sandmen to capture slaves.
- There are gem gardens where they grow rare games.
- 1st Maze: A maze of arches and balconies full of thousands of slaves. Shining gems are mounted high on the columns of each archway.
- 2nd Maze: Tunnels and rooms blocked by stones that must be shifted in the proper sequence.
- 3rd Maze: Huge, identical halls mirrored with polished metals. There are huge blue mirrors, some of which are secret portals.
- 4th Maze: A reverse maze where you have to walk through the walls. Walking through the wrong walls lead you back to the beginning.
- 5th Maze: Made entirely of glass and walls of force. The exit is always visible. Minotaurs lurk here.
- 6th Maze: The walls and floors shift like puzzles and tesseracts. Looking at this place is said to provoke madness or petrification.
- 7th Maze: Many tiny tunnels for creatures a foot tall or genies in gaseous form.
- Other Titles: The Fountain of wealth, the Stone Sultan, the Carver of Destiny, Balancer of All Earthly Accounts.
- He is hefty and has a quick wit
- He is interested in alchemy, mining, and metallurgy
The Khan's throne room has mirrors that reflect his image so that you can't tell which one is the real Khan.
- He asks constant questions
- Anyone who comes before him are supplicants stripped of wealth. His audience should be humble and poor.
- Those who come before him must make gifts of their riches.
- Mortals must refer to him as "The Magnificent." Other dao are "your radiance."
- His empire is vast and profitable
The Free Market: You can buy anything here, especially slaves. The market teems with slave traders.
Iron Crucible: Near the mazework is a fiery mountain of molten metal. It is link to plane of fire. The dao come here to trade with efreet - slaves in exchange for magic and precious metals. If you sail on the liquid, you can go the plane of fire or back. Yakfolk sometimes charge tolls in the lava tube tunnel.
Yakfolk: There are a lot of yakfolk here. Up until 5th edition, the dao were forced to serve them. The yakfolk buy slaves to make sacrifices to The Forgotten God in the "Manner Elemental" - They bury people alive daily.
3rd edition has all sort of cool things in weird places, mostly Dragon Magazine. Every once in a while they'd do an elemental-themed issue and they're all really good.
3e Web Enhancement
This page has information on a ton of Forgotten Realms gods. There is an entry on Grumbar.
Grumbar: King of the Land Below the Roots, the Earthlord. He is worshiped by underground races and "those who resist change."
Dragon Magazine 293 - The Elemental Planetouched
Earth Genasi: This race is patient, stubborn, and contemplative. Many are descendants of creatures from the Elemental Plane of Earth. The rest are descended from deities of earth. They have earthlike skin, eyes like gems or black pits, a gravelly voice, iron gray hair, and a metallic sheen on their skin. They can cast pass without trace once per day
There is also a note that there are natural portals to the Elemental Plane of Earth in the Spine of the World mountains in the Forgotten realms.
There's a whole article on elemental wolves. How random!
Shard Wolf: Wolves that were swallowed up in fissures created by an angry spirit of Earth. They're made of sharp, jagged stone that looks like shale or flint. Their eyes are pure black and they are ponderous, slow, and deliberate. They actually speak Common.
They usually appear after an earthquake or a a violent tremor. They hunt gnomes and dwarves. They have a special power:
Quaking Howl: Their howl is a 15 foot cone that has effects like the earthquake spell.
Dragon Magazine 306 - By Evil Bound
Earth Demon: "These chunks of demonic earth are simpletons even by the standards of the elemental demons." They can assume the form of a featureless rock or as a human-shaped statue of a demonic horned warrior. Its face is permanently etched into a leering grin.
They make for bad guardians, as they fall asleep at their post. Their blood is like lava, so melee attacks might cause the attacker to take some fire damage.
Dragon 314 - Dust to Dust: Magic of the Earthborn
The Earthborn is a lawful neutral cult who worship a creature they call the Earthen King. Their king is asleep and they want to awaken him. They believe that their king is on the material plane, but that his true home is in the Elemental Plane of Earth.
- (lvl 2) Earthen Grace: This spell make damage from stone sources nonlethal. That is tricky to translate to 5e rules. I could you could just say the caster has resistance to these attacks.
- (lvl 2) Mountain Stance: The caster can be rooted to the ground and cannot be moved.
- (lvl 2) Stonemantle: You can make an object strong like stone for 10 minute per level.
- (lvl 3) Tremor: A minor earthquake that disrupts spells, knocks people prone and stuns them for a round.
- Ring of Earth's Grasp: Gives bonuses to climbing, grappling an anything involving your grip.
- Staff of Earthen Might: This staff is loaded up with earth spells, like transmute rock to mud, stone shape, etc.
Earthshaker: Spellcasters who specialize in earth. They have tremorsense, they can cause tremors, create geysers (!) and at the highest levels, make earthquakes.
Dragon Magazine 347: Princes of Elemental Evil
Ogremoch: There's a big section on how Ogremoch teamed up with the Queen of Chaos (she's the villain who is involved with the Rod of Seven Parts). Yan-C-Bin, Evil Elemental Prince of Air, was an ally of the wind dukes. Ogremoch let he Queen use legions of earth elementals. He actually showed up at the battle of Pesh, the battle where the rod was first shattered.
Ogremoch wants access to the Great Dismal Delve because it has a lot of portals to other planes. He has a truce with the dao, who hold a grudge against him for some ancient slight.
Ogremoch had a dwarf warrior ally named Kaylef, but he fell out of favor. Kaylef wanders the Elemental Plane of Earth wreaking havoc.
Elemental Hazards: Well this is cool! This article has tons of useful stuff that can be encountered in the Plane of Elemental Earth:
- Adamant Algae: Dark red liquid that doubles the normal healing rate. It's also known as "Blood of the Earth" and many battles occur over control of the stuff.
- Choke Mold: Bright yellow mold which sucks up oxygen. If you get within 5 feet of it, you begin to suffocate.
- Ghost Tunnels: Natural passages that appear and disappear. Obviously, passing through one is dangerous and deadly. Make a save or basically you are sucked into stone and crushed.
- Iron Coal: Coal that burns without smoke. This stuff is pretty valuable.
- Mineralmites: These things weaken stone. Some call it "rock rot." Crossing a floor with rock rot means a save or you fall into a pit that is d10x5 feet deep.
- Pure Ore: Really nice, quality metal that is twice as strong as the normal kind.
- Silent Stones: These pebbles absorb sound. Areas with a lot of silent stones create a silence spell effect. If these are taken to another plane, they crumble to dust in a month.
- Stoneshrooms: Chalky fungus that releases spores of breathable air and creates air currents throughout the plane. Eating one is the equivalent of an entire meal. For the next 24 hours after eating, you can hold your breath for twice as long as normal.
- Magma Monolith: Not much to them, really. 40 feet tall, ooze magma and they punch you.
- Magma Element Rhinocerus: It is formed entirely of lava.
Then there's elemental weirds.
Elemental Weirds: Elemental weirds look like beautiful women linked to an element. They have magic powers, are oracles, guard portals and are bound to a certain area. Earth weirds warn of impending doom.
Earth weirds have a cold calculating mindset. Future events are the same as past events to them. To meet with them and gain their knowledge, you must bring them the skull of a thousand year-old lich crushed to powder or a stone that has never been exposed to any sort of light.
They lurk in lightless chasms, mountain peaks and barren tunnels.
Basically, a water weird from the 5e monster manual is an immature, "lesser" water weird. They will eventually become one of these oracles. We also get some magic items:
- Gloves of Burrowing: These are made from the hide of a xorn and grant the ability to burrow. Once per day, you can mold stone like clay.
- Sling Boulder: Wow, a magic sling boulder. I don't think I've ever seen one before. This one turns into a giant boulder in mid-air. They can only be used once each.
Manual of the Planes
Vezzuvu the Burning Mountain: A primordial that is trapped in a field of radiance, partially phased out of reality.
The Head of Balcoth, the Groaning King: A primordial with a face of ash and cinders that is buried in a cave, unable to muster his power until he can re-form his body.
The Keening Delve: Not far from City of Brass is this mass of blood-red rock. This is the ancient stronghold of a dead primordial named Haemnathuun. Those who travel in it hear echoes of his dying screams. There are slaads and elementals here, driven mad by the echoes. There is a crystalline heart at the center that could bring Haemnathuun back to life.
Plastron of Tziphal: This is an artifact - a breastplate of dark stone. It merges with your flesh to turn your skin to rocky armor like plate mail. It hates the gods and wants to bring Tziphal back to life. Tziphal, a primordial, isn't really detailed. He is apparently dead and is buried in a place called Mountain Builder's Burrow and is staggeringly huge. It's a mini dungeon in the book.
The Aviary: There is a 15 mile pocket of air that is home to winged elves (Avariel) and their city. Visitors can rent pairs of wings.
Caverns Under the Stars: This is a pyramid chamber 30 miles to a side. The upper half of it looks like the night sky. It is a sprawling city ruled by Geb, a deity married to Nut, an Egyptian god. There is a portal to the plane of Elysium here.
Irdoc Morda: Iron archons rule this earthmote. Their leader is the Twice-Forged General. They are building the largest spelljammer ever conceived with an iron hull to launch attacks from. There are deposit of new types of metal that makes archons behave weirdly. There are 3 watchtowers armed with scrying magic.
Pillars of Creation: These are massive columns that may hold up an entire plane. There is one that is a jagged tree of crystalline minerals, and another that is a column of muck.
Heroes of the Elemental Chaos
Primordial Shards: These multicolored crystals might be remnants of fallen primordials. They are made of crystallized ichor and have powers like magic items. They can bond with a mortal and turn it them into an elemental, partly of wholly.
Tablet of Ad-Baraz: Etched onto this clay tablet is a list of names, the identities of those primordials defeated in a time now largely forgotten.
An elementary look at the planes
Forgotten Realms wikia has a great page of concise details
The "I" series of AD&D adventures