East of Canterlot, past the Foal Mountain’s icy slopes, past the Hollow Shades, past the verdant farmlands north of Fillydelphia, one finds the Endless Ocean.
It is not, strictly speaking, endless. It is only two thousand miles across, but when the first ponies reached this shore, refugees from the fall of Dream Valley, they had never seen such an expanse of water. It stretched across the horizon, still warm even in the depth of winter, and in its rolling waves they felt the ocean’s inexorable strength, its vastness. They fled from its creeping tides, from the stinging salt spray and the soft sucking sand beneath their hooves. They found other places to build their cities.
Today, ponies no longer fear the ocean. They tread its beaches and fly kites in the constant shore breeze. Foals play in the sand, building castles and watching the waves devour them. They gather seashells and driftwood and imagine they are treasures.
They were treasures, once.
* * *
The ocean’s waters are turbid and opaque. A pony who stands in the waves cannot even see as far as her hooves; the foam and silt conceal them. The water hides all it touches.
Sometimes, ponies will keep swimming, long after the bottom has dropped out beneath their legs. A few hundred yards offshore, the tips of the waves obscure all but the tallest trees back on land. Ponies who swim this far can no longer hear the shouts of foals on the beach. They hear only the churning waves and the cry of gulls overhead.
Some swim further out, a mile now, and only a faint smudge on the horizon remains of the rest of the world, visible when the bobbing waves reach their crest.
Ponies are not renowned as swimmers. Their hooves make for poor paddles, and although their lungs are deep and their endurance endless, they cannot swim forever. Eventually they will sink, and leave behind the air and the land, the sun and the stars, the wind and the light, and they will plunge into the depths. The water around them darkens rapidly. If they look up, they see the surface world fade and disappear, and the sun is a single solitary star flickering between the waves, here and gone, here and gone, and lost.
They are blind in the land of night. The water presses all around them, crushing them with darkness, and they can no longer tell down from up or sense the depths into which they are falling. Nothing remains but the black ocean.
And if they live long enough, as they near the ocean floor, they may see a faint glow tracing the crevices and canyons beneath them. They may see points of light dancing just beyond the reach of their hooves.
Aquastria is the last city of the seaponies, but it is thousands of miles away, off the west coast of Equestria. Out here, offshore to the east, there are no cities anymore. The largest empire to ever exist, sprawling across thousands of leagues beneath the waves, is gone. Only fragments remain, scattered here and there along the ocean bottom or cast like driftwood upon the beaches far away.
Ponies who come here now, who sink to these depths, have found the heart of that lost empire. The lights they see, shimmering all beneath them, are the edges of the Starlight Trench.
* * *
Legends tell of the Tide Queen, the second-to-last ruler of the Starlight Trench and the millions of seaponies who lived within its coral mazes. Hers was a long line, stretching back thousands of years, before terrestrial ponies ceased their migrations and built the first cities on land. Her rule was gentle, the pace of life slow. The seaponies were content, and they lived in harmony with the other races of the deep -- the mermares, the whales, the kelpie, and more.
The queen and her court lived in an enormous palace crafted from mother of pearl, thinner than an eggshell, clear as glass, pregnant with all the colors of the ocean. The castle stretched for miles along the Starlight Trench. Entire cities grew within it, floating amidst forests of kelp and the rocky salt pillars that suspended its high ceilings.
Where once this palace filled the Starlight Trench, only a vast and empty canyon remains. Far below, embedded in the silt, one might find thin shards of nacre, curved like the shell of an egg, so brittle they break at the barest touch. They are all that remain of the palace, and soon even they will be gone, ground into sand or consumed by the snails and worms that crawl through the muck.
* * *
Legends tell of the Tide Queen’s four children -- three daughters and a son.
In her final years, the queen set a challenge for her daughters: whoever could secure the greatest boon for their people in the course of a year would receive the coral crown. The other children must bow to her and acknowledge her as their sovereign.
The eldest daughter, a siren pony whose scales shone like pearls, set out to live amongst the whales. She swam with them for a full year, crossing the ocean from pole to pole, and from them she learned to sing. Her voice filled the waters of the Starlight Trench when she returned, and the Coral Court wept to hear her. In the land of night, no artwork had such a reach as song, and this she taught to her people.
The second daughter, a lionfish pony whose mane was a dozen striped ray fins, swam to the shore. She called up to the pegasi spiraling above, and for a year she lived bobbing on the surface, speaking with them, learning of their world and sharing hers. She brought back to the Coral Court tales of far-off cities made of rock, of ponies like gods who controlled the stars. She was the first ambassador of the seaponies to the walking world, and she laid the first stone in the bridge between the land and the ocean.
The third daughter, a sailfish pony who swam like lightning, sought out the sharks and marlins. She found the fastest fish in all the seas, and she joined their races. For a full year she raced, and when she returned she brought back the spirit of friendly competition. She gathered all the peoples of the seas and founded the first great games to test their skill and strength and to crown a champion.
And so the daughters appeared before their mother the queen and bowed to hear, ready for their coronation. Each was confident that their gift would win them the crown.
And then the son arrived.
He was a barracuda pony, smaller than his sisters, narrow in body and snout, with tiny fins and a wide jaw filled with needles. For the past year he had lived with the mermares, the carnivores who dwelled in uneasy peace with the seaponies. The mermares saw in him a will to power; he saw in them a means to an end. And during the year while his sisters built new friendships and treasures for their people, he plotted. He made pacts, and when his family had at last assembled to select a new queen, he arrived with his army.
The seaponies had never known a king, and the son decided he would not be the first. Instead he styled himself emperor, not merely of the seaponies but of all the ocean. He blinded his sisters, slew his mother, and took her crown for himself.
* * *
Scattered throughout the Starlight Trench are broken statues. There are thousands of them, half-buried in the mud, and there must be thousands more sunk or shattered into pieces too small to discern. In some parts, where the undersea currents are strong enough to sweep away the silt and mud, the statues cobble the floor of the trench, a long road through the darkness, beginning in nothing, ending nowhere.
The statues are all the same: a barracuda pony, his lips twisted in a sneer of cold command, his stone eyes judging the empty wasteland all around.
Some statues are more or less untouched, as though they escaped whatever force had broken their kin. Along their bases are inscribed faded lines in an ancient script, so old and debased that no ponies today, not even other seaponies, can decipher it. Whatever wisdom they once contained is lost.
Not a single inscription is fully intact. Even on the few unbroken statues, those otherwise unblemished, a single word has been obliterated. It is chiselled out, or smashed, or scored, and not in one statue out of the thousands littering the Starlight Trench can this word be read. It has been erased from history.
Aside from the worms and snails and crabs, the statues are the only inhabitants of the Starlight Trench. All the rest is water, and darkness, and dancing points of light, drifting just out of reach.