When it comes to creatures in fantasy, authors can be really imaginative. There are the ‘classical’ creatures like werewolves, vampires, dragons and many others and authors (including those of computer games) seems to be able to create several more with different place on the scale between any large beast and human. Or just really scary beasts with some slight sentience.
The fact that I started reading a bit more seriously only two years ago might be a factor, but so far I have yet to encounter a book that would use elementals, let alone in such scale as they are used in World of Warcraft. That is despite the fact that creatures related to the four elements appeared in old myths (ancient China, Greece) and some others are most likely inspired by them (Russian Ded Moroz – (Great)father Frost or other examples from Slavic myths).
For some reason, I quite like the concept of a being that is made of a primal elemental power. Depending on the author’s choice, they might be chaotic to the point they attack anyone in their path and thus adversaries shrouded in myth or they can be guardians of nature’s balance, only dangerous to those who would threaten it.
Elemental’s power is usually related to the corresponding element, as is their appearance and the place where they can be found – fire elementals around volcanoes, earth elementals in caves, frost elementals in permafrost and water elementals especially in the oceans. The approach to how they can be (if even) destroyed can vary as well. They can be completely immune to their own element or only vulnerable to the opposite.
My personal approach
As I like the concept, I decided that I’ll include elementals in my own fantasy, picking the different parts of the different possibilities when it comes to their properties. I chose the guardian approach for elementals as a base, making them protectors of the places untouched by civilization. When it comes to their durability, I decided to go for lifespan in (at least) thousands of years and limited vulnerability.
As for their “immunity” to physical attacks (sword cuts, etc.) I took an inspiration far from fantasy: T-1000 of Terminator movies. Cutting an elemental with sword will cause the wound to slowly seal itself with no lasting damage and even cutting off a piece of it will not have lasting effect.
As I see elementals as manifestations of primal magical energy, disrupting that energy can harm elementals. They are somewhat resistant to magic with two exceptions: the same and the opposite of their own. The first means that en elemental can be destroyed by siphoning their power to fuel magic of the same type (like consuming a frost elemental to create massive snowstorm) or by feeding them so much magic of their own type that they incoming power overloads them to the point that they disintegrate in shockwave of magical energy they held at the moment of their demise.
Damaging them by opposite type of magic works in the way that the magic negates itself with the elemental’s magic, consuming the power in the process. Destroying an elemental by force will have the side effect of angering any nearby elementals that will try to avenge their fallen kin. Using any other type of magic than same or opposite will cause damage but destroying it that way is a long way.
When en elemental is destroyed in any way, or expires naturally, it’ll leave its core behind. The core is much denser concentration of the magic that created it and could be used by skilled mage as conduit or even source of power until it is completely exhausted, which will cause it to disintegrate. It can also be destroyed the same way as the elemental itself.
Apart from that, elementals can be created magically, usually by massive spell being interrupted before it is finished and the gathered energy, now being without anyone to direct it, coalesces into an elemental. These are much less stable (as they did not go through the long natural process to mature) and quite hostile but expire quickly.
And lastly, for the final thoughts, I personally see a total of eight types of power (magic) in these pairs for the purpose of defining the opposite: Fire – Water, Air – Earth, Life – Death and Shadow – Light.
I could add thoughts about some other things like sentience of elementals or my thoughts about creatures half-way between an animal and elemental, but I’ll leave that for some other day, so this is it from me this time.
And if someone reading this knows a fantasy book where elementals play a role, feel free to mention it in the comments. Any other comment or question on the topic is welcome as well.