This elemental plane is a plane of endless ice and cold, home to the coldest places in the multiverse.
Depending on the cosmology of the world, this plane might be a plane unto itself, part of some other plane, a place where the planes meet, or some other variation on the theme.
In at least one variation, the plane is described like a giant iceberg, bobbing on top of the Elemental Plane of Water, with a top with great mountains that reach up to the Elemental Plane of Air, with the majority of the plane being a solid block of ice in the center (with occasional cracks, fissures, and caves running through it that adventurers can survive in).
Not surprisingly, the plane is cold, likely representing the extremest possible cold in D&D. Even creatures protected from cold take damage from the harsh environment here, and temperatures can dip near the heart of the plane so that even creatures immune to cold damage take cold damage anway -- a cold so deep that "even ice freezes."
The plane is also growing, trying to close up gaps and cracks, forming new ice quickly, covering anything that stands still with a thick layer of frost, and anchoring it to the plane itself, and then slowly crushing it with the weight of even more ice.
The plane has a clear gravity, with "down" being towards the Elemental Plane of Water, and "up" being towards the Elemental Plane of Air. This has the effect of enabling frequent and dangeorus avalanches and landslides, especially if any heat (such as from a fire or torch) is introducted to the plane. This also means that climbing, flying, and mountaineering skills come in handy.
Fire brought to the plane also can freeze solid, or even become coldfire -- a black flame that sheds cold instead of warmth.
Avalanches are frequent, and may happen whenever a sudden pressure, loud noise, or heat source appears.
Sinkholes occur in places where the ice -- while seeming solid -- has actually become slush. These sinkholes trap those who step on them with freezing water and slippery edges that are nearly impossible to climb.
Areas of "True Cold" can appear when the temperature dips, freezing light, fire, ice, even things like sound, thoughts, and abstract concepts like "nearness" or "sadness." These things regularly become part of the plane itself, though explorers have been known to search for specific thoughts or concepts amongst the glaciers. Even nonspecific concepts can find a market amongst the wealthy and flashy, and, after being frozen, these frozen things act much like any other liquid, giving rise to items like "vaporized prayers" and "liquid courage."
Elementals of ice -- sometimes called ice paraelementals, or ice archons -- are the most numerous inhabitants. They form kingdoms and encampments, and most are at least loyal in lip service to Cryonax, the Prince of Evil Ice Creatures. Frost giants and ice and frost trolls also dwell in their own kingdoms or marauding bands, using igloos and shelters of snow to protect themselves from the worst of the cold. The immoths, rare though they are, also hail from this plane.
Arctic creatures that are used to cold inhabit some of the warmer regions. Normal wildlife such as polar bears and penguins, but also rarer beasts like winter wolves, yeti, ice toads, and remorhaz. White dragons can also be found here in fairly good quantity. Certain segments of the plane are deadly and cold to the point of sterility even for these creatures, however, suited as they are to the temperatures of a normal world.
Cryonax, the Prince of Evil Ice Creatures, is one of the most potent entities on the plane, and most creatures bend to his will at some point.
Albrathanilar is a an elder white dragon, perhaps one of the oldest and most powerful of that species. She works against Cryonax's influence with spies, agents, and subterfuge, since she is unable to tackle him in direct combat, but most assume she is playing a risky -- and ultimately futile -- game.
The Precipice: A region of the plane that borders the Plane of Wind. It is filled with tall mountainous peaks and thick glacier walls.
The Sea of Frozen Lives: A regon of the plane that borders the Plane of Water. It is an undersea realm with floating icebergs drifting aimlessly about.
The Stinging Storm: A region of the plane that borders the Plane of Salt. It is an endless hail of acrid salt water.
The Frigid Void: A region of the plane that borders the Plane of Vacuum. Darkness and emptiness dominate the region.
The Fog of Unyeilding Frost: A region that borders the Plane of Steam. Super-cold vapor here are breathable, but may freeze inside the lungs.
The Shimmering Drifts: A region that borders the Plane of Lighting. Snow here drifts and scintillates beautifully, but travelers become lost and confused easily here.
Teliggin: A town that reportedly sells lenses through which you can see sound while on the plane, due to the plane's slowing effect even on noise.
Ytharior (aka The Bloodmire): A region where there was once a great battle, which is now a frozen lake of blood, littered with the corpses of creatures frozen mid-battle, within the blood and atop it, extending the moment of freezing forever, with shimmering, grisly beauty.
The Sleeping Ones: These are said to be massive creatures -- many, many miles from end-to-end -- entombed within the Plane of Ice. Many have clambered among their limbs and have been completely unaware of it, thinking of it only as an unusual mountain or outcropping. Explorers who have stumbled on the graveyard of these entities have gone mad from simple exposure to it. The kuo-toa, among other races, say that these entities are creators of reality, who have sealed themselves within the ice for some unknown reason. Some say they lie dead here, others say they simply lie in wait for the time in which they will awaken again. Others, of course, say the whole thing is the work of some over-active imaginations.
- The Material Plane