There are Elemental savants that can wield the might of a force of nature, the whole breadth of a prime element, to do their bidding; casters of such raw, direct control that can cause their enemies to combust with just a few words and gestures, leaving nothing but immolated victims in their wake, or cause the very earth to shudder, robbing foes of focus and footing, or command wind currents of such ferocious power that each moment becomes a challenge to retain one's grasp or be abducted sky high. or summon waves that crest above the tallest trees before crushing down.
Being an Elementalist requires a small spark of talent, a lot of focus, and an extraordinary amount of study, normally, as everyone attempting to understand an element must study its every aspect, internalize its very nature, perceive its every pattern.
It's not impossible for someone to seek the ways of more than one Elements, but dividing ones focus and study to forces so different - sometimes anthithetical - is very taxing to one's mind and requires exorbitant amounts of study, so few attempt to delve into more than one, perhaps two, elements.
Fire is the path of devastation and he who commands the Eternal Flame is the bringer of absolute mayhem and ruination. Often called Pyromancers, those that study the element of Fire are very dangerous opponents, because the majority of their spells are both devastating to most living beings, and very difficult to avoid. Some Pyromancers thrive on an environment of open flames, and can direct all of them at once, enhancing them with raw power, condensing them in a single moment of devastating blazing fury that hungrily consumes all available fuel - whether that is alive at the moment or not - as they go out in a blaze of glory. Allies of Pyromancers that revel in the use of such spells know to give them their space, for the flames are not discerning...
The magic of Water grants access to a diverse collection of powers, much as the fluidity of water itself. Powerful waves can crush, strong currents can carry away, cleansing cascades can purify, and soothing streams can even heal. An Aquamancer studies control and emulation of water in all things, and bodies of water sometimes respond to his presence. Contrary to common belief, however, Aquamancers do not require the presence of natural water in order to be effective combatants. Whether called from nearby bodies of water or summoned from the very essence of the world, they can condense water into massive waves that crash upon their enemies and drag away fodder.
Elemental Air is an ambiguous path - amorphous, sometimes subtle and sometimes violent, sometimes invisible and sometimes perceivable from miles away. Aeromancers can be of any cut, and they can be as subtle as whisking arrows out of target or as vulgar as to pick up whole armies in a tornado. All things considered, Aeromancers often keep their real power hidden until needed, and many delight to exploit enemy weaknesses in the most efficient way available to them.
Mastery of Earth is the means to slow or even stop a whole army's advance, open crevasses on the ground and bring down structures with ease, so those with a military background or intentions to join such often attempt to study it. Terramancers become resilient and resolute by the nature of their studies, and their protective powers enhance those traits even more. Although perfectly capable of tending crops and building structures of earth and stone, the overwhelming majority of Terramancers are employed by armed forces - any strategist will mention that controlling the field of battle is halfway to victory. With capabilities that can both protect against massive projectiles and reinforce structural integrity, and hurl massive projectiles and collapse structural integrity, it's a matter of course that whichever side of a siege has a Terramancer often is victorious. Few speak of the cataclysmic devastation that results when both sides have one.
There is no strict selection of spells for Elementalists to choose from. The elements present themselves differently to each person, and perception and understanding changes the outlook - and the outcome - of any studies. Elementalists strive to achieve an effect, and they may succeed, or come up with something relevant. Or fail spectacularly.
Several schools do have structured studies that allow for at least basic representations of some of the most common effects to be uniform in understanding, and thus the end results among their students are functionally - and visibly - identical. Experienced Etherweavers can often gleam where someone has studied by observing the effects of their spells.
Although active Ether weaving is by far the most effective way to command an element, Elementalists that delve into the art for long enough find themselves internalizing more than mere understanding of their chosen element. Pyromancers find themselves more resistant to heat, Aquamancers find their need to breath mostly suspended in water, and so on. Occasionally, such effects change them obviously as well, such as an Aeromancer's footsteps being inaudible, or a Terramancer's skin taking on the texture of stone.
Although such abilities only result in alienation from the common people, they are often a mark of respect among Etherweavers - truly venerable ones can potentially give a visage of almost a true elemental creature, and such is testament to their inner power.
Although many Elementalists eventually attempt to dabble in more than one elemental disciplines, many find nothing but failure. Others, the most serious, devoted ones, manage to understand a second element enough to produce a few spells for it. Some consider this a different kind of trick to throw their enemies off balance, sharpen a focus, or ameliorate a weakness, but very few attempt to touch a third Element, or a fourth. It's not unheard of, especially among the eldest Etherweavers, but few have the patience and focus to understand and internalize opposing forces.
However, the combination of different elemental aspects on a single spell is the stuff of myths and fables, whispered in apprentice halls and laughed about in master laboratories. Such suggestions are nothing but frivolous, after all. But even if someone, somewhere, has, by some kind of absurd miracle, managed to create a spell that combines two elements, it is still certainly impossible - firmly in the realm of fantasy - to combine three of them. The notion itself is preposterous, and most Elementalists won't even discuss the ludicrous concept of combining at least two opposing elements. And, of course, the combination of four elements, two opposing pairs, is so unattainable that it is inconceivable.