The “great wheel” cosmology of Dungeons & Dragons was not something that particularly concerned me until the introduction of the Planescape campaign setting, and even then its impact was confined largely to extra-planar adventuring within official game worlds and products. As written, the “blood war” seemed an enticing concept, but the differentiation between demons (or daemons) and devils was not something that I cared for. Nor can I say that the four elements as discrete planes of existence really made much sense to me conceptually. Whilst the illustration that adorns the cover of the first edition Dungeon Master’s Guide, depicting adventurers doing battle with an efreet on the Elemental Plane of Fire in the vicinity of the City of Brass, which “can be seen floating over a flame-swept sea of oil”, is evocative, it hardly speaks to a realm of existence primarily comprised of the element of fire. Indeed, such an idealisation of the elemental planes of existence is less than readily imaginable, mainly because the four elements hardly describe everything that there might be in existence, nor clearly define what exactly they do encapsulate. This, of course, led to such things as the para-elemental planes in second edition.
Elementals as monsters are initially found in the Chain Mail Fantasy Supplement, using the traditional earth, air, fire, and water typology. Interestingly, at this juncture air elementals were almost entirely synonymous with djinn, and fire elementals with efreet. That is to say, they were imagined as conjured spirits closely associated with a particular element, but not necessarily exclusively comprised of that element in the way they literally later came to be; they were also divided into two classes, those subject to flame (earth and fire) and those subject to lighting (air and water). All four types are impervious to normal attacks, but have different movement rates and fighting strengths. The air elemental has a move of twenty-four, fights as four light horse, and adds two to its dice score in aerial combat; the water elemental has a move of six on land and eighteen in water, fights as four light horse on land, but as four heavy horse in water as well as adding two to its dice score in such combat; the earth elemental has a move of six, fights as four heavy horse, and adds one to its dice score against earth-bound opponents; the fire elemental has a move of twelve, fights as four medium horse, and adds two to its dice score against fire using opponents.
It would seem that the fire elemental is the odd man out in the above schema, as its abilities rely not on the environment, but the attack forms of the enemy. By the time of Monsters & Treasure (1974) djinn and efreet were separated out from the elementals. The elementals were rendered more powerful than previously in terms of hit dice, which vary in number between eight, twelve and sixteen, depending by what means they were summoned. As before, the combat effectiveness of the earth, air, and water elementals increases if fighting in a favourable environment, but the conditions for the fire elemental are reversed so that it does more damage against normal opponents than against fire using enemies. This suggested that affinity for fire made one less subject to its attacks, rather than more vulnerable as a result of using its element. Movement rates remain the same except that the speed of the air elemental is increased to thirty-six. As with Chain Mail, elementals will run amok if not successfully controlled. The advanced versions of elementals are very similar, the main difference being the requirement to use magical weapons +2 or greater in order to be able to harm them.
Many other creatures are native to the elemental planes, and the Monster Manual alludes to the existence of beings of greater and lesser power or intelligence not documented, but the elementals seem to be the “purest” standard form. However, the idea of creatures and places that purely exist of one element is more limiting than it needs to be, and when it comes down to it fire seems fundamentally different from the other three, in that it is largely energy rather than substance. In perhaps pseudo-philosophical terms, earth, air, and water can all be hot or cold, and their form may change by the application or absence of energy; creatures eat, drink, and breathe, and they are hot or cold, but energy is active on each, rather than separate. At first it seemed that an “ice elemental” might fill the gap, but frozen water is not an opposite of fire. Reading around the subject it seemed that perhaps Buddhism might suggest a solution in the form of void as a fifth element, but that has more in common with the Aristotelian conception of aether as a sort of heavenly substance than with the presence or absence of energy. Indeed what is translated as void from the Japanese godai (五大) system is better understood as a form of divine or pure otherworldly energy.
Nonetheless, the more prevalent usage of void and connotation of cold suggests another possibility within the cosmology of Dungeons & Dragons, which is to say the negative energy plane. Indeed, it is possible to conceive of the planar layout as a three-part cylinder with the energy planes extending it in the two opposite directions, negative and positive. These would not represent physical places, however, but rather how negative and positive energy might relate to the other three elements, or states of being. The City of Brass could be located on a plane of existence suited to seas of fire, pitiless wastelands, and dry, hot air; an environment typically hospitable only for certain sorts of otherworldly beings, but visitable by those with the means, or misfortune, to find their way thither. Inhabitants of such a place would not normally be natural creatures, but rather spirits of varying powers, whether diabolic, angelic or somewhere between; garbed in terrestrial raiment, they may appear to be composed chiefly of earth, water, or air (or metal or wood, for that matter), but their true form might appear more like a burning white fire or an icy black void. The idea is that the physical manifestation of the spirit need not be a reflection of its nature.
These thoughts are admittedly incomplete ramblings, and present their own problems in equating heat with life and cold with unlife, whilst associating them with good and evil respectively. In its own way it makes sense for otherworldly evil beings to be closely associated with negative energy in Dungeons & Dragons, since clerics are able to turn or command them. But, by that logic, an evil cleric ought to be able to “turn” living creatures and good clerics be able to “command” them, though I suppose that is not too far from the truth. Still, part of the point is to allow elementals to be potentially more than simply the brutish personification of one of four elements and become more akin to the djinn or efreet otherwise closely associated with them. Whatever the case, a plane uncompromisingly comprised of a single element does not represent much of an adventuring locale, nor does it seem to correspond with renderings of the elemental planes, so that concept can be usefully discarded. As envisioned here, then, a void elemental would be a neutrally aligned spirit comprised of negative energy, exuding cold, and perhaps manifesting as an icy blue-black flame; a draft version of this monster can be downloaded here.