My herdmates, specifically Nightmare and Luna asked me to try to explain my magic as best I could and to save time I wrote it all down. They wanted me to teach them once they learned unicorn magic and my magic have many similarities so I tried my best at teaching them, but it seems to either be exclusive to me, I'm not a good teacher, or they are having too much trouble separating their magic from the one I use. The following is the best I could do to explain it all.
The elements are water, earth, fire, wind, lightning, light, dark, and arcane, and there are several secondary elements and element combinations. That much they knew already, but I felt it was best to start from the beginning anyway. I suppose I should start with the most well known and used in this world: Arcane.
Arcane is magic in it's purest form and used in everything ponies do. Unicorns use it to shape the world around them, but need their horns to do so. Pegasi use it in while flying, manipulating clouds, and manipulating weather. Earth ponies use it for their strength, endurance, and farming. The main difference isn't what it's used for, but who uses it and how, I'll start with the unicorns. Unicorns at best can mimic what I do, same as the others to some extent, but unicorns are closer in that regard. Where I freeze the moisture in the air to make ice, they have to spread their magic and lower the temperature only managing to freeze physical objects.
Arcane is the root and all the branches from the looks of it. Pegasi use it to add more power into their wings to make up for their small size, it is converted when a pegasus repeatedly jumps on a cloud creating lightning or rain, and somehow makes clouds solid if that hasn't been implied yet. Their magic takes shape under specific circumstances, but they seem to be in control when such things happen. Earth ponies I already stated, with all this information taken into account I believe each race has a specific attunement if you will. Arcane and if the princesses are anything to go off of Light and Dark with differing attunements to other elements seem to be for unicorns. Pegasi seem to be naturally attuned to wind, lightning, and strangely enough water to a small extent. Earth ponies seem to be strongly attuned to earth with strangely enough some light, specifically life element. I believe if these races learned to channel their arcane energy and not just use it if that makes sense they could be so much more. Earth ponies could become near indestructible or grow entire farms in seconds, pegasi could wield the power of storms with ease, and unicorns could really only improve on what they've got.
Each pony would have a limit that can be very obvious just from the name or cutie mark, Twilight would be very strongly attuned to arcane, Celestia and Daybreaker would be arcane, light, and fire, and Nightmare and Luna would be arcane, dark, and water. Others like Spitfire would be special cases as she would be wind and fire or an earth pony guard named Sunlight Blade (your thoughts are the same as mine) would have some attunement to light and fire or if this would be like Dark Souls he would be attuned to lightning, or a thestral named Cold Heart who would probably be attuned to dark because his heritage, wind, and water. I will be using other sources as reference for some of the following.
Water is as I can describe it, will itself. It can be calm or raging, it can be frozen, cold, warm, hot, or evaporated. While some knowledge on fire magic would be needed for such a thing it is still deadly even without. If used right can be a source of energy or a tool in more ways than you'd expect. While I haven't tried these myself, I could use it as a blade in a sense as back in my day we used it to cut through steel because of the force behind it. If one series from back then called Avatar is right about one thing it might be able to heal people, but light, life, and divine healing will always be better so if I try that it will be out of curiosity and not a desire to use it. Water is more dependent on force from what I've seen.
Earth is well, I can't really describe it as well as I would want. It is unmoving, it is resolve, and under most circumstances unbreakable. Have you ever heard someone say something like 'his is a heart of stone' or 'his will is as strong as iron'? It is strength and ones resolve in one of the purest forms. An adept at using earth would be hard to knock down, tank most physical attacks, and hit several times harder. Also using Avatar as a reference the user could have a very well trained sense of touch and be among the most aware, a little blind girl was among the best earth benders because she could feel vibrations made from ants crawling at least 50 ft away. She could even tell when someone was lying by feeling for changes in their heartbeat, earth is adaptable to say the least, though mostly suited for defense.
Wind is freedom and potentially as adaptable as earth. The user could fly, increase their own speed, create strong gusts of wind like I did in Ponyville, or act as a near impenetrable defense and deadly offense. It's kind of hard to block a weapon you can't see and pierce an invisible shield that shreds anything that gets near it. It's also among the least violent as the user should be able to pull the air out of someones lungs or move the wind at such speeds it prevents oxygen from reaching the person in the middle of it. Of course it still has it's weaknesses as it's more speed and dexterity based than the others. Applying the kind of force I mentioned is hard even for me, and I technically invented it.
Fire is several things. It is emotion, ambition, it could feel like a little heartbeat or it could be an inferno, but the key factor behind it is breath. Most might hold their breath during a strike, fire requires the user to 'build and store energy' then release it. Think of how dragons breath fire, it would be kind of hard to do so without air. While breath is required, it is fueled by one's desires and emotions. A conquerer who is absolutely livid and well trained in fire could possibly defeat a dragon at it's own game.
Lightning is energy and also very difficult to use and thus more dangerous than the previous ones, even referred to as 'cold blooded fire' in Avatar as well, but I managed to master it. It requires a calm mind and constant steady movements, but can be bypassed at the cost of weaker spells. Once generated it will need to be moved at a constant pace or else it will launch itself in the direction it was moving last, think of it as energy being passed around and once an opening is made it releases itself. For anyone but a master the lightning will simply blow up in a person's face if they are not calm, the mind doesn't need to be empty, but the user can't be angry, excited, or nervous.
Light is self explanatory, it is positive emotion, thoughts, and memories. It can heal, protect, and if necessary purge or even bend the light around you or make it pass through you doing something similar to camouflage. To be honest, I was terrified when I first used it. I felt like how a child would feel getting scolded by it's mother one moment, then just as fast it changed to excitement, joy, and pride. I was so confused I didn't use it for months, then when I tried again I re-experienced several memories, all the good moments and highlighting any with Misty. When it finished I was crying as I felt like everyone I ever loved was right there in that moment. Users should keep this in mind when using light or dark: 'the line between light and dark is so very thin, be certain you know which side you're on'.
Dark is also self explanatory, but it is entirely dependent on the user. That shadow could be your friend, or your worst nightmare, where there are shadows there are weapons, where there are people, well let's just say it's very dark inside the body. To me it felt like an old friend, one who has always been beside me. It is the same as light in several ways, but takes it a step further. Where light would purge a necromancer, dark would protect the necromancer depending on how and why they use it. A necromancer who uses condemned criminals and dead animals for self defense or acting as a 'grave warden' and protecting graveyards while letting the dead rest peacefully is more likely to be protected than a necromancer who makes a zombie plague to help him rule the world. To use dark, one would need to fuel it with negative emotions, but unlike light, it's base power never decreases unless you will it to, a person who has only known pain, hate, and rage will be much stronger than an expert, but will still lose due to inexperience. There are several risks to this though, if the user has not confronted and beaten or acquired the willing assistance of their 'demon' they will be weaker and more vulnerable to it. I bypassed this as I embraced my darkness and rejected the light years ago, but I found a new light later. Those in the dark will learn one simple truth and it's that the real demons are inside us.
Now we move to the secondary elements: metal, polarity, blood, heat, chaos, life, divine, death, abyss, ice, soul, and void. These are all the next stages or combinations of magics. Metal and polarity (magnetism) are the next stages of earth, shaping metal and controlling it such as slightly changing the course or speed of your opponent's sword.
Blood is mostly just water manipulation inside a body, but can become easier if there are enough of certain magnetic minerals such as iron in the blood and ice is a little easier to make if you have some knowledge of fire magic as heat is taken away thus creating ice. Heat as I've said is fire, but manipulating the temperature instead of creating a souce of heat, this can confuse pyromancers for cryomancers though pyros won't be able to use the ice anywhere near the extent of a cryo.
Chaos, life, death, divine, and abyss magic are really just varying degrees of fire, light, or dark combined with arcane. Life and death are self explanatory, but death kills using different methods such as poison, decay, pestilence, or just sudden death while life can stop and reverse it all if the person still lives or if the soul is still linked to the body. The more color in the eyes the better.
Abyss and divine magic are the 'primordial' light and dark. Comparing dark or light fire to abyssal or divine fire would be comparing a candle to a forest fire, and unlike dark fire, abyssal burns can't be healed without divine magic, and divine flame is only as deadly against what the user defines as evil. Abyss magic also attacks the soul of the victim and the user user if the user isn't careful, but divine would be able to heal this. Chaos is just a crimson colored and more powerful fire that only got it's name from Dark Souls, though these flames are strange in a way I can't figure out, they are adaptable to an extent as I've made green, purple, and blue flames depending on what is being combined with it and how much of each is added.
Soul magic is believe it or not equal in power to abyss and divine in raw power, but more costly as it draws from your own soul, specifically the power in it. Aside from feeling drained faster in exchange for more power the user wouldn't have any problems. While VERY dangerous, the user can disconnect their soul from the body and either explore or 'connect' with other souls and any number of things could happen. The user can try to kill the person, they could switch bodies, enter another's mind, or find refuge in another vessel.
Void is hard and simple to explain. Depending on the user's emotional state there will always be very faint traces of light or dark magic, if the person has a clear mind their emotions will be easier to control, if the emotions are 'shut off' they will draw from the void instead of their own magic or soul. The void is the hardest to use because of this as the 'door' is either wide open or shut locked tighter than Fort Knoxx, but the power is so vast and great it doesn't seem to have an end, as if the void is power itself. Fire that will never burn out, earth that can be shaped into anything from anything and become indestructible, water that never changes form unless willed to, ice that won't melt or break, true blood manipulation, lightning that doesn't need a container and gives seemingly infinite energy, wind that can cut through anything regardless of velocity, the void can also erase anything, even erase injuries and possibly erase or undo someone's death thus achieving true immortality and resurrection.
The void is for lack of a better way to put it the end or a never ending cycle, it could end said cycle. Time and space are irrelevant, foreign concepts to the void, it just exists yet it doesn't, it's very existence is a paradox. 'Power without reason is nothing more than a will for destruction', as I said it IS power, but the lack of emotions can easily take a turn for the worst for without emotions we are left without desire, necessity, and morality, all we have left is memory. To truly be hollow would be to become as bad if not worse than how I was once, and I left my own mother for dead after having witnessed her get mugged by a guy with a knife. What better way to gain power or prove you are stronger than to not just kill, but erase, return everything to nothingness? A true Void mage would either exist simply just because, or would be the destroyer I chose not to be.
I fear this power so I have only used it for mere seconds at a time.