The elemental planes are relatively close to the Material Plane. The warmongering leaders of the fire plane raid other planes for slaves and glory.

Like most other planes, distance and direction does not have the same meaning as it does in the Material Plane, and all planes have a defined center. The further you go from the center, the wilder the elemental forces becomes, until you reach a different elemental plane. These border-regions are dangerous, but contain powerful magic. The planes form a circle, with water and fire on opposite ends, and earth and air also opposite each other.

Muspelheim, Elemental Plane of Fire

Hot, desert of black sand dunes, lava rivers and volcanoes.

City of Igneum

The city at the center of the plane. Ruled by Surtr, the Pharaoh of Fire, a primordial Fire Giant who commands armies of giants and efreeti. Azer slaves are plentiful, as are slaves and servants of other conquered races.

A river of lava flows through the city, providing heat to furnaces and other industries. Fire giants make up the ruling class, bolstered by efreeti soldiers and slave-drivers.

Palace of the Pharaoh

The great pyramid palace is covered in shining black stones. The surrounding complex has many buildings decorated with arches and domes. Several thin spires poke at the dark sky, but none higher than the peak of the palace itself.

Surtr receives audiences in a large throne chamber at the center of the pyramid, lit by flowing lava. He stands over twenty feet tall and wears a robe of rich crimson. On his completely bald head is an open helmet of obsidian, set with bars of ruby. This headdress is the foremost crown jewel of his royal house. He wields a crook scepter, wrapped with black leather.

Odin has foreseen that Surtr will invade Midgard at the time of Ragnarok, when the planes will intersect and the gods will do battle on the mortal plane.

Portals to the Plane of Fire

A volcanoes or hot springs might contain a permanent portal to the fire plane. A temporary portal could be either the result of, or cause of a forest fire.

Vatnaheim, Elemental Plane of Water

Endless ocean. The settlements lie on the shallower parts of the seabed. Coral reefs, kelp forests and deep ravines hold many dangers. Chief among them is Jormungandr, the World Serpent, who will come to Midgard during Ragnarok and devour all life in the oceans.

Skyfarheim, Elemental Plane of Air

The center of the Plane of Air is a collection of islands, floating on clouds in an endless sky. The largest island, Aetheria, is the seat of the Emperor Yan-C-Bin, who rules over a myriad of princes and nobles, all vying for power in an intricate game of favors and counter-favors. All beings who make this plane their home must know their place in society, or risk offending those with power.

A giant thunderstorm encircles the plane of air. It is the source of many dangerous lightning elementals and other dangers, who sometimes comes close to the floating islands near the center. If you fall off the islands, if you are not caught in the magical winds that howl throughout the plane, you eventually end up in either the great ocean of the Elemental Plane of Water after falling through the freezing reaches of Frostfell, where air and water meet, or you fall into the black sands of the Fire Plane, after passing a great firestorm at the border of the planes.

Politics

The emperor Yan-C-Bin is not as powerful as one might expect, as most of his political clout is tied up in making sure he stays emperor. If the elector-princes are unhappy, they could replace him. Yan-C-Bin sends his servants to find magical artifacts which he gifts to electors in order to keep them in line. If a pretender showed up with richer gifts, why would the electors keep the current emperor around?

Portals to the Skyfarheim

All thunderstorms carries some of the power of Air, and a powerful one probably contains a rift across the Bifrost to the Plane of Air. Adventurers from the Material Plane had better come prepared though, as where they end up probably does not have solid ground.

Myrkheim, Elemental Plane of Earth

Great cavern systems, with swamps and bogs and small cities. The least civilized of the elemental planes. Further from the central chambers lies unexplored tunnels, filled with gems and riches but also dangers.