"Ten thousand years did Twilight rule, and well. The world knew peace, and harmony, and friendship. Not uniformly, and not constantly, but those problems which arose were overcome, the threats that appeared, defeated, and life was good.
"But ten thousand years -- no, of course it wasn't exactly ten thousand on the dot, do excuse me for being poetic -- ahem. Ten thousand years is a long time, and new threats did arise. Eventually, one of them got lucky enough that... there were no alicorns left, after it was defeated. Much of my own power, I invested into the sun and moon, that they would keep circling, if not so annoyingly regularly as before, with no device to break or group of unicorns to fail, and even if something happened to me. Obviously unneeded, as it turned out, but having just lost... well.
"In any case, the various peoples of the world proceeded to muddle along as well as they could with what they had, and to their credit, it worked, for centuries. But without Twilight, each generation drifted a little further from her teachings. The dragons and changelings, with their long lives, best remembered, but as Twilight's ideals began to stale around the world, as corruption slowly increased without her at the core, this proved too little to turn the tide.
"Dragons have strong instincts, and adult dragons have great physical and magical strength. Those instincts are far from insurmountable, far be it from me to discriminate against someone for the inclinations of their magic or biology, but the fact was that once a dragon did begin to lose faith in Twilight's harmony, to see it fade in the world and decide to take advantage instead of trying to fix it, the old drives to take and hoard readily welcomed them back. It was only a few dragons, at first, but those who kept faith had few options for stopping those who didn't, without further damaging that faith themselves. Those dragons who turned to petty crime were easy to simply arrest -- well, not easy, but not an ideological danger -- but the clever ones? Those who found ways around the written laws, who couldn't be legally attacked, or at most could be given a slap on the wrist? How to stop them, without some young dragons taking the message that "harmony" was merely another expression of the rule of force their blood had already whispered to them about when they heard about those fallen dragons' wealth and power? Only a few, only a few, but a few and then a few more over time adds up.
"The changelings, now, they stayed the purest the longest. Never really stopped practicing Twilight's teachings at all, in fact, last I heard of them. But all they did was talk. Tell the dragon robber barons that Twilight wouldn't approve, when the tycoons had already cast off all care for Twilight. Tell the nonponies who looked at the increasingly corrupt international order centered in Canterlot and went straight to wondering, and speaking about, why their kind should have to deal with others at all, and how much simpler it would be if they didn't, that some -- absent pony should still be what they base their own lives on. Tell the ponies increasingly looking for for their own little tribes and local groups to remember the glories and follies of the past, when the former were past, irrevocably so, and the latter, well, they knew better this time, and anyway, the windigos were all dead long ago. The changelings were too scared of what they might do if they stopped just talking, were too afraid that if they resorted to subterfuge and force again, and it worked, they'd just keep going.
"As actual wars began to break out elsewhere in the world, they were seen less and less often outside their own small territory. They were still happy to welcome visitors, and for a while their hive was the last pilgrimage site of those who still followed Twilight's teachings. They took in as many refugees as they could, too, when there started to be refugees who needed to be taken in by someone, but their resources, even bolstered by donations for the remaining faithful, were limited. And eventually, neutral or not, a tiny country fully of pacifists and refugees, its mundane resources strained just supporting its population but who knows what ancient secrets locked in its vault, proved to tempting a target.
"No, it doesn't really matter who; they're just as long-dead as their enemies, now, and both sets of descendants equally guiltless. You want pure historical integrity, go find an archaeologist, if those still exist.
"In any case, from what I heard, most of the changelings escaped, somewhere. Took some of the refugees with them. The might still be hidden somewhere in the world, though I... did have concerns about what sealing magic would do to such magical creatures. Perhaps they fled all the way to another world, joining the breezies, or S-- Ah, well, that would be getting rather off track.
"Oh, yes, breezies exist. Existed. Probably still do, might want to look around for a portal opening up, if this lasts... well.
"In any case, things were getting increasingly bad, but I suppose I can't look too harshly on the changelings, given I was in much the same boat. Moreso. They could only wonder what their rule over the world would be like, and fear the unknown. Whereas I, I have the distinction of being the one and only creature to ever hold this world entirely in my absolute power, for ages uncounted because I forced time itself to make them uncountable!
"...But I did not really like who I'd been, then. And I could not be sure that, if I placed myself so far above other people, I'd keep seeing them as other people, or... relapse. And so I, too, talked, in my own way. Tried to at least guide the increasing chaos along productive, or minimally harmful, courses.
"Eventually... that too failed. Each escalation produced further destabilization, great need and grounds for the next. Perhaps the world had simply been as it was too long, with even me converted to Harmony, that some... cosmic balancing principle forced matters. I have wondered, for a long time, if things could have been different.
"But in the end... something was done. I will not say what, or who by, for it was as offensive to my nature as it was to my adopted beliefs, and deserves to be forgotten. It left the world in ruins, those few parts which were not already dead, dying. And yet, too many of those remnants just kept fighting each other.
"And so, at last, I stepped in. Irony of ironies, I myself seized the Elements of Harmony, and I fused their power with all but the last of mine. A great spell, sweeping over the world. Healing, and changing. Some of those changes were minor -- you may be interested to know, for example, that in the old days, unicorn horns were mostly only found on unicorns -- but key was that since you, ah, your ancestors, had used magic to destroy the world near enough to as soon as you didn't have someone responsible watching over you, I'd take that magic away, until such time as someone new appeared to match... Twilight and her friends. If anyone ever could.
"And the world recovered. The land and its creatures slightly different shapes, but growing again. Conflicts, limited, simply because there was no other option. I was disappointed by not by that point surprised that you seemed to be dividing yourselves along tribal lines again, but, no matter. I had done all I could for you, and if you still insisted on squandering it and the gifts of your past heroes, that was your problem.
"I had enough of my own power left, just enough, to preserve myself against both time and most would-be lethal threats, and to, if not all in an instant, make this comfortable little nostalgic hidey-hole for myself. I would wait here. I would remember, even if every one and thing else forgot. I have had, over the long centuries, the occasional visitor, but only the occasional. Given the family resemblance the phantom wings and horn it doesn't stretch to, I can only guess that the activation of the key crystals I felt recently was in one way or another the success of my most recent visitor before you.
"But if you think being some approximation of an alicorn is enough to impress me, hah, I have seen the real thing. I have ruled the world, and been bested, and spent millennia by the side of those ruling it better than I did. I have tried to save the world, and I have destroyed what was left of it, when that failed, when mortals brought themselves and everything else to ruin. I will not let things get that far again. So you can come to me for advice, and for ancient stories. I would appreciate hearing news of the world, in return; I don't get out as much as I used to. But if you want to rebuild this world, see that you succeed.
"Because if you fail, I'll be waiting. And you're a fool if you think the Lord of Chaos has told you about all the tricks he has up his sleeves."