Historical Endnotes
1. The appearance of the Shila and the official founding of Equestria probably took place within 20 years after the events recorded in the Hearts-warming Eve account. Best estimates put this event maybe 1,300 years in the past from 'present day' Equestria.
1a. Of those approximately 1,300 years, the last approximately 1000 years saw Lu (Princess Luna) trapped as Nightmare Moon. She was rescued perhaps 4 years ago by Princess Twilight and her new friends.
2. The Shila's carefully worded rallying cry the day of the Cougar invasion did two very important things for the realm. It gave the realm it's permanent name -- Equestria. It also helped three bickering factions see their fundamental same-ness, and forged them as one. They never fought among themselves again.
3. The tracing of the Phantom Alicorn's Cutie Mark was not from a tombstone, but probably from some sort of commorative stone-work. Also, Shila was indeed not a proper name, it was a title, meaning 'Deliverer'
4. Other Pegasi had seen Shysage and his family relaxing up on the natural cloud bank near their capital city. The city of Cloudsdale was soon founded. Since the realm was now one, this was not a problem. In fact, the presence of a heavy military up in the clouds formed a substantial deterrent. Even if all the ground based military were taken out, the attack from the sky could still be brutal.
5. Now working together, Equestria expanded rapidly out from their capital city. And they all worked together with this expansion. Soon there were so many ponies that, after a few more overwhelming defeats at the hands of mighty stallions, the Cougars stopped invading, and were never seen again in large numbers.
6. The Portal was in fact first charged by the magic of the Shila, who was actually brought back in time by the Portal itself. There is no known way of explaining how time wrapped around upon itself to accomplish this feat.
7. The Shila raised the King's two daughters, always conversing in the language current in Equestria from the distant future. The presence of these two daughters, as Princesses, quickly transformed the language of the realm from the 'Old Pony' form to the current form, which has remained stable for over a thousand years.
8. This note was added later.
The history book Cel gave Shysage proved to be a historical treasure trove, and will be further developed at some point. It was written in 'Old Pony' and would take a while to work out.
Still, it became quickly clear that the ascendency of the Pony Nation in Equestria was foretold well in advance. It was likely that the Cougar's surprise attack, and escape with the King's Mare and his two daughters (the two 'appointed ones') was intentionally meant to put an end to any dreams the Pony tribes may have held.
The Cougars clearly didn't read any further.
The arrival of the 'Shila', the Deliverer, was also foretold well in advance, including both the rescue of the King's daughters, as well as raising them as her own. Her role in helping crush the next Cougar invasion was also mentioned specifically.