The Plane of Air

Centuries ago, in a forgotten world, a particular dark wizard and a student of necromancy managed to overwhelm all opposition to his rule, until only a handful of old magic-users and elderly priests remained with any sort of power to protect their people.... and they knew that if they tried to stand up to the Necromancer Lord, they would fail, and their charges would be killed and enslaved for all time. But they also knew that together they had the power for one vast, intricate spell, one that could reach across the world and protect those who still remained free... and so they used that power to take every living humanoid and their livestock, crops, and dwellings to the Elemental Plane of Air, where gravity depends on where you believe it to be and all things are constantly falling or flying. On vast falling terrain and levitating cities and solid clouds, the people of the conquered world settled, befriending the elemental natives and secure in the knowledge that the mages and priests' spell had locked all doors to the Plane of Air from their homeworld behind them. Keeping them safe for all time. Alas, it was not so. Ten generations have passed, and the Necromancer Lord has found a way to send his undead troops to the Endless Skies through portals linked with the Planes of Elemental Earth and Fire and Water, and the Paraelemental Planes of Smoke, Magma, Ooze and Ice. However, his portals are weak, as his specialty is Necromancy and not any other kind of magic, and each can only be cast once. The magic of the spells is vulnerable to the pure essence of the plane of Air mixed with positive energy... which is often found in a sparkling energy known as Living Lightning that trails around living beings like a pet. However, such energy is also extremely rare, and so the living and elemental races are searching (over an endless dimension of thin air) for enough living lightning to close each of the vast portals, while flying armies, powerful spellcasters and faithful defenders and fleets of skyships ready themselves to destroy the hordes of vampires, skeletons, zombies, ghosts, and other foul monstrosities.

Races:
Humans - Many have adopted the patterns of clothing and mannerisms of Arabic peoples and Europeans from the Age of Pirates.

High Elves - The Wood Elves and Sea Elves have joined forces with their cousins, resulting in a unified tribe of elves, many of whom tend to the few forests found on falling earth in the Plane of Air or study magic in gleaming towers suspended in space.

Snow Dwarves - With land so rare in the Plane of Air, the surviving dwarves have largely burrowed into icy glaciers and mountains and some solid clouds, and their hair is almost universally white as a result, though they are still brave warriors.

Air Elementals - Spirits made of living air in human form, they tend to be as mysterious as they are hard to see. They can control the weather at a will, as they are but extensions of the Plane made manifest.

Djinn (singular Djinni or Djinnya) - Beings of colored smoke and wind, they are tremendously powerful and largely ignore the threat the Necromancer Lord means, secure as they are within their beautiful and otherworldly Citadel of Ice and Steel. Their magic is unsurpassed by that of any other resident of the Plane of Air.

Niomi (singular Niomus) - A native people with bat wings growing from their back, they possess a skill for cloudshaping, allowing them to form weapons, buildings, and other substances from the stuff of clouds.

Drakes - Human-sized bipedal dragons, able to breathe various sorts of energy (fire, lightning, cold, sonic force, acid, light, darkness, water, heat, wind, etc).

Arachnial - Human-sized spiders who ride the skies in vast raiding ships woven of webbing, they are fierce pirates.

Gargoyles - Creations of the ancient religions who settled in the Plane of Air, they have kept the faith and defended the faithful for years and do not fear death.

Harpies - With human faces, torsos, and arms with the wings, tails, legs and talons of any species of bird, the Harpies are a varied race when it comes to personality, though many possess supernaturally charming voices that, when raised in song, can inspire desire, fear, bravery, thoughtfulness, and other emotions.

Sylphs - Air elementals who appear as genderless humanoids with wispy, flowing hair, pointed ears, and swiftly-buzzing wings (often those of dragonflies, butterflies, or hummingbirds), they are supernaturally swift fliers, and cannot truly be caught unless they wish it.

Entomen - Human-sized insect people, they can appear as any insect species and oppose the Arachnial. They are great craftsmen, and have special senses of hearing, sight, scent, and touch that the other races lack.