You know I once developed a really autistic elemental system, and I am still working on improving bullshiting it. One thing to note, is that I am really bad with names, most characters in my imaginary stories don't even have names, just ranks, even though I made stories featuring them for years.
In this system, there are 7 elements(pic related), three primary and four secondary(two for destruction, fire and ning, and two for creation, water and air). I call it ning and not lightning, because lightning is the combination of light + ning, and yes there's is darkning as well. An elementalist can use either one of them(most common), a primary and a secondary(earth + fire, light + ning, dark + water and so on) or two secondaries which is just fire+ning or water + air) which are rarer, even rarer are those who can use three elements like earth + fire + ning, but can not combine all three, just combinations of two. There are limits in that you can not have two opposing elements like fire and air, or dark and earth. Users of dark, mostly command shadows, whereas users of light create material light in existence.
The system is a more advanced rock, paper, scissor, where water beats fire, fire beats air, air beats ning and ning beats water, earth beats water and air, but looses against fire and ning, while dark has a slight advantage against all elements, except light and light has a slight disadvantage against all elements, except dark, which it has the greatest advantage against(a light elementalist has a greater chance of beating a dark elementalist, than a water one against a fire one, so they are a more specialized user), there is no advantage or disadvantage between fire and ning, or air and water.
Those who can use two elements can combine them, so something like fire+earth gives lava, water + earth gives plants/trees, air + earth gives sand, earth + ning, I guess life, still working on this, imagine golemns or some shit. Water + air gives ice, and fire + ning gives a new form of plasma, imagine something that is as fast as ning, but that spreads like fire. Dark combined with the destruction elements gives more powerful spells, whereas combined with the creation ones gives stuff like poison(dark + water) or miasma(dark + air). Light combined with the creation ones gives more healing, and with the destruction ones, weakens them(because light is weak against most elements) but is a good counter for someone who has dark + fire or dark + water, though I imagine light + ning, giving lighting being the fastest element in existence. Oh yeah and fire doesn't produce light(so you can't light a cave with it), only fire combined with light does that, so you need lightfire to illuminate dark places. These are called hybrid elements.
Limits like water + fire or light + dark, exist since they are impossible to accomplish in reality, as those are rules imposed by gods, and of course, in typical autism, the people of this world devised a barrier, that when erected separates the users from time, space, gravity, and all the rules of existence and reality, and now they can do some crazy shit, fire + ning+ earth, gives an element similar with lava in consistency, but is as fast as ning I call it blue lava, air + water + fire gives a white fire that spreads like fire, but freezes anything it touches, including fire, earth + air + water, gives an element that can instantly go from solid to liquid or from air to solid, it's the strongest in defense, and the same element can pass through it without friction, so you erect a wall and throw spears through it, or "water" passes through it as if it didn't exist, light and dark can also be combined with a secondary element, so you have silver fire, or silver air, it's mostly an upgraded form of the secondary element. I haven't come up with, what happens when you combine all secondary elements(fire+water+air+ning) or all primary elements(light+dark+earth), but all 7 elements combine, which nobody can do, except the elemental goddes who is dead, but it's the element of life and existence itself, all that this element touches would instantly disappear from existence.
If someone wants to use this system, they can do so.
/autism