Magic:

*Quick recap: Races have two "slots" for magic powers, "inner" magic and "outer" magic. Inner is, essentially, innate abilities, often a "stat boost" or just some simple ability that normally doesn't go far beyond themselves. Outer magic is an actual "caster" magic. Not every race has both slots filled although nearly all of them have at least one slot filled. (Examples: Humans only have the inner magic slot filled for endurance. Giraffes have no innate magic but a great deal of magical potential.)
**When a race does have both slots filled, the two magics tend to tie into each other. (IE, minotaurs inner "drive" magic which makes them such mad inventors and their outer "device" magic, which outright make them mad scientist running on tenuous grips of reality.)
**There are means and methods of moving beyond the instinctual magic, or lack thereof, of your race. This is called sorcery and is generally dangerous because of insanity-inducing black magic. Instinctual magic comes with instinctual aversions to black magic, but not so with sorcery. (This is sadly what made giraffes so dangerous.)
**Masters of the outer magic are called magi, one of the wise.

*So unicorns are already pretty well known in what they can do. They only have an outer magic, wizardry, that is in particular to them tied to space.
**Wizardry has a strength of being instantaneous and a weakness of being instantaneous, "one and done". Continuous effects must be continuously sustained.
**Unicorns, presumably other races with wizardry, can also lay down death curses which last far past their demise. It has to do with "life=ephemeral, death=permanent". Celestia managed to coddle it right out of common knowledge.

*Okay, so, pegasi and earth ponies (who were once called the arion), modern ponies know their outer magic (flight and strength) and barely have an inkling of what their outer magic (herbology and meteorology) really does or can really do.
**Those who still remember them know them collectively as druids. Earth pony magi were more the stone circle kind of druid, while pegasus magi were more the bend the forces of nature with direct communication.

*Earth pony magi, by themselves, belong to the class of magi called geomancers. Geomancers use an awareness of the natural magical background radiation, how physical objects and even physical acts affect the ebb and flow of this living force that surrounds use and how, in turn, this change affects the physical world.
**Earth ponies in particular aspects towards plants or, more specifically, the flow of magic affects plants and sometimes vice versa. Rocks are also a common focus, normally in how stone affects the flow rather than the other way around.
**There are also those earth ponies capable of interacting directly with the flow. These "rangers" can travel through ley lines, travelling nigh instantaneously, store things within folds of magic and detect the subtle changes and vibrations in the environment presaging near future events,

*Pegasus magi were classified as shaman. Shaman can sense and interact with spirits, using force of personality and/or bargaining to get spirits to do their bidding. Another example include the necromantic cows, who specifically aspect with spirits of the dead.
**Pegasi aspect towards spirits of sky and weather, but these zephyrs are savages, and they only understand one language. Pegasi don't normally speak with them normally, but just push them around. A pegasus with a powerful personality and a fast enough flight speed could clear the skies in ten seconds flat.
**Some pegasi do aspect differently than others. One might aspect towards beasts, speaking directly with their living spirits and using her compassion to tame them. She may connect her spirit with a familiar, a small unassuming animal, in which she stores all of her negativity.

History:

*Okay, so, the Celestial Wheel just went kapuut. By that I mean the massive magical mega mechanism that pulls the Sun and the Moon (really, a projected avatar for a distant neutron star). It's temporal control here on the World just catastrophically failed, heralding the end of an age, and putting the World on the knife's edge of oblivion. Again. Don't worry about it, this happens all the time.
**Enter ponies, who are just starting to evolve cutie marks, unicorns, pegasi and earth ponies, albeit this last one is less obvious than the others. Together, they manage to wrangle the Celestial Wheel under their control. Brave pegasus shaman went to where the sky ends and the void begins to barter with Sun and Moon. Industrious earth pony geomancer built vast networks that channel and bind celestial energies. Vigilant unicorn wizards constantly light the beacon the brings this vast working together.

*The pony magi are a secretive group that enjoy an elite and privileged place in society. They go about master and apprentice, teaching only the most promising students they can find, with a healthy dose of nepotism in the selection process.
**The problem that crops up is with unicorns. Earth pony and pegasus magi perform occasional maintenance on their part in the Wheel, although the pegasus shaman flying up to the upper atmosphere to carefully remind Sun and Moon of their job don't always come back. The real problem is unicorn magi constantly pouring magic into the wheel and dropping like flies with no pony to replace them.
**So unicorn do the unthinkable and they start a program of mass dissemination of their knowledge, namely opening schools to teach classes at a time, producing the number of magi necessary to maintain the Wheel. Many of the other pony magi see this as a betrayal.
**This also has a side-effect of spreading a sense of elitism among the unicorns, further straining the relationship between the pony tribes. With the pegasi able to live apart from the other, the divide was already growing and this was one more wedge that eventually led to the tribes splitting into different nations.

*Amidst this turmoil rose a pony born in Paradise Estate, the last bastion of a united pony kind. She was a freak, a genetic throwback to pre-cutie mark, pre-tribal ponies, with the gifts of none. She was named Huf, an old word for "hoof" since that was all she had.
**Huf had crazy determination though and banged her head against sorcery long and hard enough to turn herself into the first alicorn, all without managing to go bug nuts insane. In her victory over her weakness, she added "Laurel" to her name. She gave herself a cutie mark, a quill in an ink pot, a testament to how she wrote her own destiny. She set forth then, determined to convince the three nations to put aside their differences before disaster struck.
***It's Lauren Faust. It's Lauren Faust, okay? Huf is German for "hoof" and Faust is German for "fist".
**The three nations don't take kindly to some freaky mutant pegacorn preaching peace and brotherhood so she's ran out of town. While out in the wild, she touches the Celestial Wheel, attracting Sun and Moon's embodied spirits to her and they bang, giving her two immortal alicorn fillies out of the deal.

*Meanwhile, the tensions between the tribes get so bad that Discord is summoned to this world and does what he does best.
**Celestia and Luna come out of left field and friendship laser him. From there, they pick up the pieces of the tattered tribes and unite ponies under their rule.
**They also take over the Celestial Wheel, putting all the magi out of the job. The unicorn wizards, with their numbers, have sheer momentum keeping them going forward and find a new purpose. The other magi ended up fading in obscurity before nigh disappearing completely. Earth pony geomancers retained key secrets within their bloodlines and pegasus shaman disseminate only the most vital pieces of knowledge to keep Equestria's weather working functioning.

*Laurel Huf died of old age, she is very specifically not immortal.
**Neither are Twilight or Cadance, being that they were turned into alicorns. Neither is Flurry Heart, mind, since it actually has more to do with Luna and Celestia's sires literally being Sun and Moon respectively. (No, that isn't a typo)

My Super Special OCs:
(Feel free to ignore this bit)

*The Elemental Brothers (And the Warner- Elemental Sister). I dug the idea that ponies have a long history of being ruled by ageless immortals, even before the Celestial Sisters. They shared the same father, the last "normal" pony before Huf's freak birth many years later, and their mothers were elemental spirits. They led the original push for ponies' dominance of the Celestial Wheel but their innately terrestrial nature meant none of them could actually control the heavens directly. It was their influence, combined with their arrogance and vanity, that encouraged the division between ponies.
**Aequor, son of Sea, was the High King of the Unicornia Kingdom, the "Kingdom By The Sea". Influence was decided by how related you were to him. For example, Princess Platinum was his granddaughter, one from one of his many wives. When he began to willingly transfer power to the Celestial Sisters, he did so by adopting Luna as his sister, marking her as his equal. The two commonly shared their herd, influencing Luna to being the "herd" mare and influencing its practice in Equestria until her banishment.
**Caelum, son of Sky, was the Priest-King of the Pegasopolis Junta, the "Kingdom In The Sky". He was the head of spiritual matters for them but willingly remained subordinate to temporal leaders. Commander Hurricane was technically his superior, one of a long line of such superiors that Caelum naturally outlived. Caelum's subordinate clergy were all his ritualistically adopted siblings. As part of encouraging the transfer of power to the Celestial Sisters, he married Celestia, marking her as his equal. In time, they dissolved the marriage and Celestia pursued a series of monamorous relationships with mortals, influence the practice of "coupling" in Equestria and ensuring its dominance after her sister's banishment.
**Tellus, son of Land, held the ceremonial title of Merry May King within the Earth Pony Republic, the "Kingdom On The Land". He held no official power, but his actual clout in reality was significant. He spoke on behalf of the Celestial Sisters to the senate and convinced them to yield to the transfer of power.
**Flamma, daughter of Flame, was the Princess of Paradise Estate, the last remnants of a united pony nation and the future seed of a new one. She had the power to switch between tribes (perhaps she was a proto-Changeling) and acted as a diplomat between her squabbling brothers. It was why she was "Princess", so she presented herself as never being in competition with them. She was Huf's mentor and adoptive mother. She never lived to see her granddaughters but her influence remains felt, including how the Celestial Sisters chose to be Princesses instead of Queens.
**The Three Brothers, downgraded to Princes, are still around. However, a curse laid on them by Nightmare Moon sent them wandering. Only recently as the curse been broken with Luna's return. Their influence also remains to be felt, contributing to Equestria's lopsided and matriarchal view on sexes. Stallions are seen as asocial and unfit to rule. Mind, modern movements a few generations past have done much to reverse these views, but they still linger like a bad habit.

*Strife, spirit of evil, Discord's sister. In this, Sun is Order, spirit of order, and Moon is also Harmony, spirit of good, also Discord's siblings. Harmony is also a female spirit and Celestia is her Magical Lesbian Spawn with Laurel Huf, aka Not Lauren Faust.
**Discord & Strife were summoned together by the tensions between the pony tribes. Discord preyed upon the Unicornia Kingdom and the Pegasopolis Junta and Strife preyed upon the Earth Pony Republic and Paradise Estate. Strife is weaker but far more cruel than Discord. Where Discord would free prey that bests his games, even after he cheats, Strife would prove to be the sorest of losers.
**Strife is shattered in a suicide attack by Flamma. She isn't dead though, but each of her "shards" ends up interpreting her role as the spirit of evil differently.