INTRODUCTION

The Elemental Planes are a vast place, truly, and home to a vast number of creatures quite unlike those seen upon the Prime Plane. Of course, there are similarities in some cases - the mantes of the Fire Plane have their more diminutive cousins in the forests of our own Plane, after all. But then, one sees a starsucker or a cloud carrion, and the similarities end.

The fauna of the elemental planes are varied indeed, with anatomy set to baffle even the skilled mortician. But the mysteries of their origins and inner workings are not the subject of this study. For what truly sets these creatures apart is the effect they have on the environment in which they live.

ON ESSENCE

It is presently theorized that, one way or another, the creatures of each Plane avail themselves of the elemental energies there, their bodies causing the raw (and diffuse) elemental energies to coalesce within and be stored as essence, for whatever purposes they may need. It is quite possible that this serves as a substitute for normal voracious metabolism seen upon the Prime plane.

Interestingly, in some cases this seems to be harmful to the Plane and its ecosystem (such as it is), as the elemental surroundings there can be seen actively avoiding the approach of these creatures - or at the least, being transformed into a worse form by the fauna's machinations.

EARTH

The Earth Plane is divided into two distinct and immediately identifiable areas: The Catacombs of Corpus Clay and the Mountains of Madness. The Citadel of Rock is also present, but as it is home only to the Earth Lords, it is not relevant to the work and as such shall not be mentioned here.

Four sorts of creatures reside upon the Earth plane: grubs, lindwyrms, stoneghasts and gargoyles. The lindwyrms and grubs reside within the Catacombs, and the stoneghasts and gargoyle roam the mountains.

For the most part, the cave-dwelling creatures seem to have a mutually advantageous relationship with their environment. The grubs burrow through the earth, aerating the soil (for whatever that may be worth), and the lindwyrms are host to some sort of lichen that has miraculously adapted to the Tainted environment in which it grows.

The cave that leads out from the catacombs and into the Mountains of Madness is known to shift from time to time; this could indeed be a result of the grubs and/or lindwyrms, whose ceaseless excavation causes rockfalls to block the cave, while simultaneously revealing other apertures.

The Mountains' inhabitants seem to do little to or for their environs. The gargoyles subsist there, seeming content (to a point) to simply live and let live. The stoneghasts, however, have had their minds twisted by the tainted energies there, and at times will lash out at passers-by. Neither of them has much of an effect on their surroundings - this is either a testament to their lack of involvement, or a testament to the strength of the unmovable mountains.

Also of note: The gargoyle and grubs alone bear dark essence, which may call into question the theory of elemental energies being used in place of metabolism in the case of stoneghasts and lindwyrms. It's possible that lindwyrms consume the physical stone around them - which is certainly what their mouths appear designed for - but this has yet to be decisively observed. 
Additionally, the Earth plane is the only plane in which there is a specie that leaves behind no essence when slain - not one, but two oddities are found in the stoneghasts and lindwyrms.
Stoneghasts are often seen to spit a black mist at their victims; this may be congealed elemental essence that is being wasted in offense rather than being stored and cultivated.

FIRE

The Plane of Fire is mostly barren, with a patch of flame blossoms near to its ethereal gateway. While lovely, this blossoms appear to be naught more than miniature flames of their own, and lacking in any apparent nutritional value. This lays to rest the theory that the other parts of the Plane have been stripped bare of all vegetation by hungry wildlife.

The wildlife, incidentally, comes in three commonly-seen forms: the great fire mantes (or mantises), the lumbering flame hogs and the six-legged (yet reptilian rather than insectoid) cinder crawlers. All of these creatures are demonstrably capable of harboring essence within their bodies.

The environment itself has little reaction to them, and their effect upon it is negligible. The only visible disturbance made by the fauna here is the incessant shifting of the black sands at the hands (or rather tusks) of the flame hogs. Therefore, it can be concluded that while fire is a volatile thing, the ecosystem of its plane certainly is not (though the terrain itself surely is, make no mistake).

It is interesting that the flame hogs instinctually sift through the sands with their tusks. For those who don't know, this is the same manner in which the pigs of our own plane search for food. Extended observance of the hogs and the sands they root about in has shown them never to uncover anything, which begs a few questions. Are the hogs simply acting on instinct? Or is it possible that their true diet doesn't consist of elemental energy, as theorized, and that they simply haven't been observed eating before?

The theory that a standard food chain is absent here is lent credence by the presence of the gigantic fire mantes - in a normal, Prime ecosystem these creatures would likely prey upon the flame hogs and perhaps the cinder crawlers as well, but this does not occur upon the Plane of Fire.

THOUGHTS ON THE PLANES OF FIRE AND EARTH

Both of these planes seem to have a stable environment that is unaffected by its inhabitants (alternately, the effect is negligible at best - at least from what can be determined by observation). The remaining two Planes, Water and Air, seem to have a less-than-symbiotic relationship with their fauna.

This naturally leads to the question of whether or not the intrepid adventurer is doing the elemental planes a service or not by slaughtering all living things thereon (excluding adventurers and Lords and/or Ladies, of course). One might say that doing so on the Earth and Fire planes is, at most, a trifling favour for the local ecosystems.

But to do so on the planes of Water and Air certainly seems to do good for those places' natural environs. As will be detailed in the pages to come, the creatures that dwell there have a harmful effect on the surroundings - or so it appears.

AIR

The Plane of Air has little in the way of terrain, naturally enough - most of it is built on wisps of cloud above a dizzyingly endless sky. (For those having trouble grasping the concept, and who are unable to visit the Plane, simply look up the next time you are flying, and imagine that what you see is what's below you instead. Indeed, such concepts as 'above' and 'below' become rather blurred upon spending a great deal of time on the Plane of Air.)

Three forms of wildlife are here, as well, just as with the opposite plane of Fire. Cloud carrions, stormeaters and aerial stalkers are all in play upon this Plane, and all are difficult to spot with the eye, being compact in build and ethereal in form. The cloud carrion is  presented as a small insectoid creature that clings to the clouds and consumes them. Wayward shards of ice upon a cold breeze are worth another look, however; upon this plane there is much more to them than that. These chill eddies are actually the bodily makeup of the aerial stalker, the life-form that is upon the Plane of Air in greatest abundance. The winged serpents of the Plane, colloquially known as stormeaters, are the most apparent of the Plane's creatures, and also the rarest (it may indeed be no coincidence). These, too, suck upon the local clouds ravenously.

The carrions and stormeaters are demonstrations of what I mentioned earlier when I stated that the Plane reacts negatively to their presence. The clouds curl away from their predators, and the usually warm air grows cold in the presence of the dreaded aerial stalker. Why the Plane of Air developed this way remains a mystery. My best theory is that air itself is too diffuse to form into essence simply by respiration, and a more dense substitute was needed, seen in the form of clouds.

The fact that the essence these creatures leave behind when slain is cloudlike in appearance and form supports this theory.

WATER

The Plane of Water, like its counterpart in the Earth plane, is comprised of a pair of distinct areas: the Great Starry Sea and the Lake of Dreams. One is inhabited by starsuckers and the other by dream leeches, respectively.

The starsuckers' very presence is appalling, and they make their way endlessly along the blue of the Water Plane, ever drawing water into their bodies, to be used in whatever mysterious function passes for metabolism upon these Planes.

The supposed cleanliness of their waters is sullied by the presence of starsuckers, who draw the stars (perhaps more accurately, the appearance of the stars) out of the waters around them before heading off for more. While the waters of the Plane do not shy away from their presence in the way that the clouds of the Air plane do, the prevalence of stars in New Celest's symbology and culture suggests that their absence is not a thing to be desired.

The Lake of Dreams, home of the legendary dream leeches, presents an interesting quandary. One wonders if this lake is truly the source and home of all dreams that we mortals experience, or if such is simply a turn of phrase. Regardless, the dream leeches can be seen turning dreams into nightmares when feeding upon them, which is another example of their harmful (or at least, their less-than-beneficial) relationship with the Plane they inhabit.

Why is it, then, that the Elemental Plane of a place such as New Celest - the supposed beacon of hope and peace in the Basin - is fraught with such turmoil? The answer may be as simple as a look at the essence that is produced within the bodies of its inhabitants.

While water is necessary for life, it has little nutritional value beyond its hydrative qualities. To draw exclusively on it forever will lead to one's death, and the same may be said of the Water Plane's inhabitants. The essence they produce is not watery, but it is instead light essence. This explains why the starsuckers draw the light away from the waters around them - the light, not the water, is needed for their sustenance. And a nightmare, indeed, could be seen as a dream lacking light and hope and joy, though I remain undecided on the issue of the Lake of Dreams being the source of all mortalkind's dreams.

Regardless, water acts to dilute all it comes into contact with - this is likely why the creatures there suck what they need from the nearby liquid rather than taking it in large gulps. To require a processing mechanism would be a waste; there is simply too much water per unit of usable light.

IN CLOSING

It is my hope that this study upon the Elemental Planes' wildlife has given my reader some food for thought, and that the next time they venture to the aforementioned Planes they will pause to observe the wildlife there rather than laying about with weapons and spells (and without discrimination).

I eagerly await any findings that may prove or disprove the theories presented in this work.

Special thanks go to Aiyana of Gaudiguch and Pejat of Hallifax for allowing me to observe their city's Planes with impunity.