The following is an introduction to the concept of the Nether Realms as places defiend by their elemental balance and energies by outlining several different Elemental Nether Realms.
The nether realms have varying degrees of similarity with the mundane prime material world with the most noticeable differences begin the connections to the various elemental planes. A nether realm may suffer or benefit from varying degrees and energy level of elemental substance. The following describes in broad terms some of the myriad possible Nether Realms.
Ash Nether- these realms have had a (relatively) recent surge in the abundance of elemental fire which has led to a degree of ruin and ash in the aftermath of the surge. The realm is still likely to be strongly influenced by Fire but it is possible for the realm to have stabilized or eased back to it’s original balance. Smoke and still burning fires are not at all uncommon in an Ash Nether and breathing may be made difficult by the smoke and ever present ash.
Ice Nether- these cold frozen realms suffer from a dominance of Air and Water (sometimes in conflict) with a weak or lacking influence of Fire. Mountains will be crumbling under the weight of glaciers, snows will blanket all the land and all but the deepest of seas will be frozen solid.
Rust Nether- a realm of elemental imbalance where the solidity of earth and the nurturing of water is checked by a diffuse but ever-present intrusion of fire and air. Matter itself is slowly burring away by the imbalance and while not traditionally ablaze all the world will look to be burning or rusting away. Nothing but the most extraordinary will last long in a rust nether.
Dust Nether- A realm with a lack of water where air dominates the earth. Vast seas of dust are blown by the harsh winds where oceans might otherwise flow.
Salt Nether- these realms have modern lack of Water and by an imbalance with Earth and the other elements great swaths of land are covered by great crystal towers of salt, the older the realm the less of these there will be found standing (unless the realm differs from a weakness of Air) and great salt flats will cover much of the terrain.
Radiant Nether- these curious realms are created by an over abundance of Fire that expresses itself as radiant heat and other energies not simply flame. Should there be a sun or stars in the sky they will be colossal and vibrant. Beware the lycanthropes in realms warmed by energetic vibrant moons.
Quag Nether- in these realms Earth and water dominate and are in conflict with each other leaving low languid mountains, shallow silt filled seas and sodden fields. These are dreary places where geyser of mud threaten what passes for life as much as volcanoes do in the mundane world.
Dusk Nether- in these realms Fire is not absent but it is not as energetic as it is in the mundane world and as such heat is nit as warm and light not as bright. A dim dusky gloom is common during the days lit by a lazy sun and the nights are deep and dark with virtually invisible stars and a dim moon.
Metal Nether- curious realms where Fire and Earth battled for dominance (and perhaps still do) where life is formed by metallic growths instead of flesh and bone as known in the mundane world. In realms where water is not absent great beaches of rust are pounded by lead colored waves.
Morttuus Nether- these are realms where death has won out over life perhaps by a sudden intrusion or absence of elemental energy. Some realms will be long dead with little but the eldest of shades present while others will be as a recent filled necropolis sometimes crawling with the undead. Some scholars will call these a Praesepultuus realm for all the world appears buried in death. There may endure populations of carrion scavengers and ghouls if the death of the realm was recent enough (one has to wonder at the hunger of ghouls in a Mortuus Nether long after the death of the living).
Vital Nether- a world teeming with life in abundance beyond anything seen in the mundane world, beasts and plants grow upon each other and the very dust in the air and the mountains themselves are alive, the ground is writhing with vermin and the seas are filled with life almost to the point one could walk upon the surface of the waters. All the blessings and curses of organic life are ever-present in these realms where even the ground itself may bleed.
Flooded Nether- an overabundance of Water has flooded a seemingly mundane world. All that remains is likely drowned but it isn not impossible for life to cling to rafts (or arks) or dwell high upon isolated mountainous islands where earth has not given way entirely to water.
Vitriolic Nether- Water is in imbalance with the other elements in these realms and often where one would expect to encounter common water they are instead scorched by acid. In some realms life has adopted but in others it hides from the ever worsening rains that strip the flesh and flow down to sea of acid.
Anemos Nether- realms rich in energetic Air. The ever-present winds may lift whole islands up into the sky or rip away at the earth forming great delicate labyrinthine arches or have ground all but the greatest of mountains into a featureless waste.
Exanimus Nether- these realms are often mistaken for a Mortuus Nether because few last long in a sustained absence of Air. If the realm was of a different balance int he past it may indeed bear more characteristics with a dead realm but this is coincidence as while the sudden lack of air is deadly there is no negative force in play itself. Gods, wizards, and ancient civilizations may still reside in dome covered citadels that hold in precious air but the rest of the realm is a virtual vacuum.
Molten Nether- in these realms Fire and Earth are in dominance and battle with each other causing the presence of magma seas and gigantic volcanoes. Some may host cities of efreeti and demons relaxing in cooler climes. Some molten realms may have been a Metal Nether in the past and have huge melting cities or wilds covered by the steely skeletons of metallic beasts now dead.