Let’s talk djinni and efreeti.
They hate each other, are elementally themed, and as both are middle-eastern derived, share cultural similarities. Okay so far as that goes; let’s keep digging.
The djinn are air-aligned in D&D, and actually I have a hard time separating them from Bralani, who are Eladrin and thus super-elves. Both have a whirlwind power (though I thought djinn actually transformed — nope!). Bralani aren’t in 5e, so I have to stop comparing them now.
My point: I’m gonna stick ’em in a blender and co-identify them.
The Djinn hail from Aaqa, the eye of a great cone-shaped storm-cum-mountain whose frustrum-peak is a great churning sea, whose walls are an infinite downwards convecting avalanche, whose floor is an endless, flawless blue sky, and whose center is a vertical, streaming fountain from infinity, slowly filling in the overhead sky with the sea.
First, some laws: fluids are drawn in (towards the base of the everpresent glowing salt-sea “Fountain”) and towards the sea-filled tip (“up”, from the point of view of visitors), while solids are drawn out and towards the infinite rim (“down”, emphasizing spiral motion — there is no attractive point at the “base” of the Fountain; they form the Walls of the great infinite cone of Aaqa). Massive solid objects emphasize the horizontal, rotational component (and so prove more stable), and exert a gravity on their surroundings, causing fluids to reorient. Small objects spin lazily away easily once broken off (for instance: dust and sand are easily disposed of). Both solids and fluids are somewhat sticky and accretive over short distances, so harmonious aeolian rocks, rain-catching lotus-moons, barnacled cloud-whales, constructed moss-galleons or chaotic whitewater moons can prove extremely stable, rotating the Fountain and allowing solid visitors to interact with slower-flowing, orientation-sharing water on the topside (the water’s gravitationally-sticky “underside”) of the body.
Beyond the Wall, there is no space — only an infinite upwards torrent of jewel-like sand, falling to the rim
As a result of these curious physics, many stone islands acquire a spray of sea, giving them an appearance of clouds, and naturally occurring fountains are common. They also acquire hardy plants and clinging vines, which can deal with the curious properties of Aaqa and thrive: colorful succulent orchids, olives, oranges, and beautiful hanging air mosses. The animals favor bioluminescent floating cteids, cephalopods and other flying marine life, as well as brightly colored birds.
The torrent is 100% super toxic glowing seawater, dealing 1 point acid damage per round immersed to non-natives and 1d12 damage if consumed. Actually, so is the rim-oriented falling water near the Wall, in addition to running the risk of being crushed between its grinding boulders or deafened by the noise. However, by letting any sea water stand in a vessel made of the natural stone or plant life, it will form pure, clear water and sparkling float crystals, which usually fade and sink over the next d6 days.
An infinite latticework of tributaries — some glowing, some freshwater — aggregate lazily towards The Fountain; forming infinite rivers or coalescing out of miles of mist or forming from a particularly violent spring in The Wall.
The gardens, cloud-cities, palaces and gardens of the Djinn are here, where stone meets sea or where sky meets stone.
Their needs are few; their culture ancient; their pleasures vast. Some hermits of their people attain such understanding of the nature of the universe that they are called Wind-dukes or Noble Lamas, and are said to be inheritors of a great worlds-shaping power.
They claim to be the first giants, and it is true that there are many storm- and cloud- giants here, living on and within the Fountain or the Sea. Empyreans share the gardens of the Djinn. The Djinn sail the skies and waters of Aaqa, knowing the secrets of where it enters other worlds along misty shores or where ancient roots drink from it and they may dock beneath strange skies. They trade, and accept peaceful visitors, and are content in the ever-changing rhythm.
The Ifrit of Imix are pretty much the opposite of this. In every way.
D&D’s efreeti are already plenty cool. They have society, they keep slaves, they have superpowers and allies and you don’t have to feel badly for killing them.
The only think I want to change about them is to give them a link to the Djinn and a reason to be so sybaritic.
So: they dwell on a near tidally-locked world called Imix, stuck on the sun-facing pole, towards the red giant they’ve triggered spiral descent towards to avoid evernight. At the anti-helion of this sun is the Netherstar, the hole in the sky through which their sun’s life fitfully bleeds. The blackened landscape the solar flares illuminate once per century is the haunt of the Nightgaunts, lords of darkness and death.
At the aphelion lie the fields of fire, where the sundrinking salamanders roam.
At the vast, tropical borders where the sun never sets lie the lands of the ifrit: the cities of brass and the blasted, irradiated wastes between them. This is where their sultans plot for ever more power, scheme and make war, take slaves and plumb the riches and secrets of many worlds using the powers purchased from their allies in the City of Iron.
Their needs are infinite: their sky and their world is dying, their civilization founded on infinite excess, their souls traded long ago. Their markets are cosmopolitan and their guards omnipresent, the underclass of offworlders constantly on guard against kidnap and slavery, but the riches of kings available.
Further south, lie a belt of mountains contested between the giants of fire and the giants of frost; during half of every solar year — centuries in length — they invade the lands of the other and eke out a living in lands suitable to their needs, with sunrises and sunsets; during the other half the balance shifts and allies from their respective side prevail, the weather shifts, and the belligerents retreat to their fortressses and fastnesses.
Then the dark frozen lands of the south, where the weak sun rises around the horizon weak and fitful, where the snow still falls, to the frozen plains the frost giants hold.
Then, beyond the glacial peaks that hold the storm, the lands ever beneath the gaze of the Netherstar. The riches of the world-that-was scatter this plain ringed by glassy spires, haunted by Nightgaunts and their night-armies.
In the north, the Salamanders summon showers of flame, metals and gems, great boiling streamers slowly killing the sun. Sometimes from the south in the sky, a nightgaunt will break through the wall to die in the sun, boiling off soot, death and skittering shadows, also killing it.
The Djinn and the Ifrit connect when Imix and Aaqa first went into convergence. The Ifrit discovered how to tunnel into Aaqa, bursting through The Wall and rading monasteries, harnessing cloud whales to war zeppelins, and constructing battle moons whose orbits would allow raiding parties. While repulsed and their tunnel flooded, the attack repeats itself again and again: the core of Imix is somehow the peak of Aaqa, and connection between the two worlds undeniable.