Okay, now I’ve read the comic as well. Essentially, you can already find the main scenes here on the site. There is not much missing and you get the whole picture together. And even if I’m not sure yet how far this plot will make it into the show, I still have to say two things about it:
1.) Discord is not completely wrong with his opinion. But the way he acts is once again typical of him. He says one thing, does another. And vice versa. I have the feeling he believes to be in the right as always. But it also shows an incredible mistrust on Discord’s part in the ponies’ ability to keep Friendship and Harmony going. And as far as that goes, he’s not wrong.
2.) I don’t think Twilight is acting out of character by creating the Unity Crystals. We simply know too little about the crisis that was going on at the time. In Discord’s words, “Then truely things happened, much which is too frightful to describe. Things in Equestia became even more divided.“
Also missing is the entire part explaining why the three crystals were eventually separated. So there’s not really anything to spoil here. Also, a certain character (Shadowy Alicorn) is only briefly hinted at. You can already guess who that is. Not only because of the silhouette, but also the demeanor. But what is REALLY going on with the Great Pony Tribe War 14-18 TA (Twilight’s ascension) before the creation of the crystals and afterwards is not explained. So everything is again as before only pure speculation.
It looks like Twilight’s reign definitely lasted for some time. And I can’t imagine that she didn’t inform the leaders of the other races beforehand, or that she didn’t get permission from them to create the crystals. If it is, THEN this is really a very stupid writing. But we are not yet so far to be able to say that with certainty. If we will ever get certainty about it. The show seems to love its loose ends, cough, cough. ;-)
I think it’s not all the magic in the whole world, just the pony magic, Discord may have been wrong - and he is also associated with the pony magic itself by being partly pony, and can not use his chaos magic as a result. It is certain that Twilight had informed the other world leaders - and since many centuries have passed without them reacting, it may mean that only the ponies were affected.
“Great Pony Tribe War 14-18 TA”? Are these facts? Also, it seems that there were external factors behind the unrest that had occurred among the ponies, and then tried to take advantage of this, only to be stopped by the Mane 6 and the other heroes. It is possible that Twilight even had to use military force to bring order to the ponies, just as others had done before her. But here it seems that this happened because the magic had gotten out of control, with the same storm clouds as in MYM.
In the end, the Mane 6 won, but the damage was done, they had realized that the emotional instability in the pony magic has become so strong, that it must be prevented. The non-ponies that may have entered into a loose world order with Equestria will undoubtedly put the Mane 6 under strong pressure, along with large parts of the Ponykind who only want peace and security. Twilight may have tried to remove the problem only to realize how profound it will be when dealing with the very essence of the Ponykind. Then this had to be sealed away, with a kind of “dam”, and together with her friends she took the magic from the ponies.
What happened was that the focal points of the magic of the ponies, had been moved and united into a single focal point - the Unity Crystals. Thus, all magic became subject to a collective. The Unity Crystals can act not only as a door, but also a dam where it is possible to counteract the harmful effects. It was not the best solution, and the spell that was probably Twilight’s masterpiece in her life was an emergency solution. But the Mane 6 had no choice, for this surpassed all they had encountered.
It was not a good ending, but it is the writers behind G4 who must be blamed for making such a scenario possible, especially by making the magic very fragile, erratic and far too easy to manipulate as when Cozy wants to remove all magic. There are underlying tendencies towards anti-magic where the magic is denied by fear, and this had repeatedly emerged, most recently in S10. A “mature” magical world was deliberately made as unrealistic as possible.
The G5 will thus be about repairing the pony magic and making it safe again to continue the course of civilization for better or worse. Although Mane 5 would like to continue to have magic, Zipp is skeptical about whether this can be justified in the face of possible disasters, and Sunny in mind may have thought that it is a bit reminiscent of coercion aimed at the ponies. Like Mane 6, they need to think about their people and their world in relation to magic.
A human being will automatically give up magic if it is not possible to reconcile with human nature. Star Wars with the emotional division of the Force comes to mind, everyone saw what the consequences of this were in the SW universe with constant battle without stopping in the millennium after the millennium, the “light” against the “darkness”. In MLP, on the other hand, it is a question of having, with the risk of doom, or not having and surviving.
The magic needs to be fixed. There is no other way out.