Millennia ago, before the Sister's Reign, before our present Nations took hold, even before Harmony rose, each land was ruled by a being of great power.
The gyphons, a fledgling empire, had hold over the highest of mountains, and consisted of little more than a raiding army and the lands they pillaged. It was not until after the Fall of Nations that they began to build something more than the raided highlands, into the mighty empire they hold today. In their time, they were lead by General Gideon, Marauder of the roosting-lands, and his lineage before him.
The deer, withdrawn to the Whitetail woods, were a reclusive and almost forgotten race. They had no true leader, but their most guarded city was presided over by a Stag called Cedar the White. Little is known of him beyond his incredible military defensive strategies, but it still holds to date that he was among the most prominent of his kind.
Among the dragons there was no single land they called home, but rather wherever the sun burned hottest they lay to rest. Few interactions recorded by them remain to date, but one name has pervaded through the ages by virtue of infamy alone; Fork-Tongue, one of the smallest of her kind, who had built the largest of hoards with a silver tongue and an army of lesser dragons and mercenaries. To date, her hoard has not been found, but is documented to be somewhere among the plateaus of the Badlands.
The-Land-Beneath-The-Land is the widely accepted name for the once-great Diamond Dog Kingdom, but to them it was called the Underealm. It stretched for miles, linking the north to the south, east to the west, and a far safer travel path than through the Badlands or Swamps. They would have attained a monopoly over trade, and became one of the richest of the Old Nations. This Kingdom was the domain of King Bandit and Queen Stella. It's entrances have been lost to the passing of ages.
From across the sea had traveled the minotaurs, who sought to stake a claim in the new land they found through trade. They had only begun to get their hold on the continent before the collapse. While there is no currently known location of their short-lived port-city, the goods and technologies they brought with them are still valued and used today. Their city had only a single ruler in it's short existence, a distinguished and sophisticated minotaur by the name of Silver Scales.
Among these great Nations a number of other races were to be found. The Buffalo, Changelings, Goats, and the various races of Ponykind. None held a true place in the world, none held their own land to call home. They were the refugees of nations unwritten, of times unrecorded; little to nothing is known about where they originate.
And then, over the span of a single decade, each of the nations were all but eviscerated. Kingdoms crumbled. Nations broke apart, let themselves be overtaken by the rebelling groups. The nature of the world itself was thrown into madness, the dawn of the Age of Chaos. A single creature rose to power, proclaiming himself "Discord, Lord of Chaos."
It is unknown the precise length of his rule; The days and nights grew inconsistent, clocks stopped, rewound, fast-forwarded. Most records of times before then were destroyed or distorted beyond use. It was not until the Age of Harmony began, with the end of Discord's reign...
Twilight huffed in frustration, closed the book and pushed it aside. Despite the title 'Ancient Nations', the chapter on them had almost no help whatsoever. Not one book in any of the ancient castle's libraries had told her anything about their fall. She'd found nothing in Canterlot, and even Celestia herself knew nothing about what caused them to crumble. Neither her nor her sister had even been born at the time.
She stood up and walked over to the balcony, looking over Ponyville. This town hadn't even existed in those times. It'd been nothing, just an empty plains dividing Whitetail Woods from the Everfree Forest. It was strange to consider how none of these buildings and structures had even been thought of back then. Nopony around to conceive them. Not even Celestia, and there wasn't anyone older than-
She blinked. Then blinked again, rushing back to her books. Discord had started his Reign in those times. He was around before them. Why had she not thought to ask him about it yet?
"Ask me about what?" an innocent voice inquired.
She swung around to find the draconeqqus in question holding a stethoscope to where her head had been. "How long were you listening to my thoughts?"
"Oh, just a few moments. I was in the area, thought I'd drop by for some light reading." he replied, picking up one of the books only for it to float aimlessly upward. "But what was it you wanted to ask me?"
Twilight gestured to the stack of books on her workbench, and the note-riddled cork board hung up behind it. "I've been reading everything I can find on the Pre-Equestrian nations, but I can't find any reason that they would simply collapse like they did. I was planning on asking you what you know."
The book fell heavily to the floor. Discord quickly flew up in front of her, with a grave expression darkening his face. "What do you know about that?"
Twilight flinched, but continued uneasily, "There isn't much information on what happened. Only that the leaders just... abandoned their nation. They didn't even give note of it, and the nations never bothered to pick new ones. They just turned on themselves, some even were destroyed completely, and that pretty soon after that, you just took over."
Discord was visibly relieved, and drew back from her into a reclining position. "Ah, I see. You don't know anything at all then?"
"No..." she trailed off, eyeing him with suspicion. "What do you know, then?"
"Me?" he said, pulling what he thought was an innocent face. "Nothing at all!"
She glared at him. He kept up the face. After a moment, the draconequus gave a sigh, and turned away, towards the balcony. She circled around front of him, and was surprised to see his expression was that of regret. She'd only seen it once before, and it took Tirek's rampage to bring it out.
"Discord," she asked hesitantly. "What do you know about their collapse?"
He gave an uncharacteristically melancholy chuckle, walking slowly out onto the balcony. "I know everything about it. It was my fault."