Hello, this is a spoiler warning for the whole EqG franchise, If you have yet to watch the movies or buy any of the merch, please stop the reading and do so. You Have been warned.
Welcome, I am gamer_km and i am to try to explain what the F*ck is magic in equestria girls. So buckle up, bunker down and prepare to be amazed at how much I can explain Let’s begin.
To understand the magic of the EqG universe, you need to understand what is causing it. The elements of harmony, or the macguffins of plot convenes as I call them, are 6 magic fruit that came from the tree of harmony, they are used as a super weapon against anyone who disagrees with the main cast. They act as a focuses to amp up the magic of the users via a spell matrix, before being shot out of the Element of magic.
“What spell matrix? Are you trying to tie in Fallout Equestria here too”, I hear you yell. No, not quite, the elements are kinda like a computer network or an assembly line, as the magic is pass through an element, the user adds their magic to it making it bigger and stronger. Then it reaches the user of the element of magic to cast the spell. This is best demonstrated when they summon discord (https://youtu.be/mcrRDScGvEo). Anyways let's get back to the topic at hand.
In the first movie Sunset steals the element of magic, and Twilight and the human 5 use the magic of “friendship” to defeat her. But that’s not quite the case, yes twi’s relationship with the human 5 did play a part, but it was twi that did most of the work. Look at this screenshot (http://orig05.deviantart.net/2877/f/2014/278/8/5/equestria_girls_defeating_sunset_shimmer_by_rainbowtwilight29-d81qbp0.jpg) of them as the use the magic, and when they protected her just before the element linked back to twilight. Both times they made a magic circle.Twilight saw that the human 5 did in fact reflect her friends, and when they blasted sunset, the magic started at twilight and traveled backwards to fluttershy.
“So why did they get pony ears and stuff then the elements blasted them?” You say, well the elements have a template, what they recognize who can wield them, Twilight’s element being made from the other 5, has a master template of them. When sunset puts it on the element went “Ok, this person has strong magical potential, and I cannot see other elements, let give this use access it” hence why sunset’s body corrupts, it’s now in a form that can easily use magic, And when twilight and party “go oh shit, we got to stop her” their hearts aligned and the element of magic saw this and associated a template with a person, then grated the ability to channel that magic.
It tried to turn them into horses, but stopped because they had a good sense of self as a human, and don't want to be in an alien body. And as the magic passed through them, it left a small part of it behind, permanently changing them. In the weeks after the first movie Fluttershy and Rainbow dash would have seen weight loss, Aj and Pinkie, a jump in muscle mass gained. And rarity would have more energy. Why? Because that magic is still there, trying to match a preset that their minds wouldn't allow.
So what about 2ed movie, well, We are going to throw friendship out the window here, because this movie is about music, what’s a harmony? Well according to webster's it’s “the combination of different musical notes played or sung at the same time to produce a pleasing sound” Among other things, they are using instruments to invoke a harmony to the point where they seemingly are able to summon the embodiment of harmony to laser friendship at the sirens. this is also why Rainbow dash “ponies up” while no one else does in the Im awesome song, because it is reacting to her magic, and ego.
So onto the 3ed movie, Well it’s really all sci twi’s fault here, she is opening rifts between worlds. Allowing more magic to come into their world, and what did the elements do that season prier, used the Elements of harmony to restore magic to everypony. That is a still lingering spell afterward, a hole opens in reality and the magic sees that there are ponies with weak magic here, it’s going to fix that. So the get a power boost, then sci twi’s magic compassion eats it, And at the end the same as the first, both Twilight and sunset go into forms that are better to use magic, she seals the holes then confronts twilight, their magic cancels each other out and they move on, twi getting PTSD in the process on top of her new magic.
Movie 4….well they had 3 other times they used magic at some point, it’s building up in them, when gloriosa uses the Element gems she found, it left a residue that the human 7 magic absorb, It gave them enough of a push to give them powers akin to their elements. Because of damage to the portal the stones are connected to the tree, acting as a counterpart to the real elements, so when they get them, human 7 get a power boost. Maybe they are harmony seeds?
Who knows?
If you, Liked this Let me know, I may do it again.