Thousands of moons ago, Nightmare Moon attempted to overthrow her sister. Even more moons prior to that, Starswirl banished the Shadow Pony. Even more moons ago prior to that, Skyros existed.

But millions of moons ago? There was a dynasty that spanned the entire continent of Equestria. One that can be found deep deep underground, past slate after slate of compressed rock. Almost every cave in the modern Equestria won't reach far enough down for a pony to explore it.

And some human ended up there in the land preserved by a spell, buried by a spell, and kept still by a spell.

Almost still.

Tags updated as it goes along.