Her subjects think too highly of her.

Without Luna, they began to elevate Celestia's status. They began to pray to her, swear by her name, idolize her actions.

In their eyes, she is a god.

But for all her power, Celestia is not a god. She never asked to be one. She did not decide who lives or dies, or ordain the flow of time, or cause good things to happen to her subjects.

And yet they praise her supposed deity. And after every celebration, she cries, for Luna's fears are coming true.

Prophecy

Even to ponies as powerful as Celestia, the gift of prophecy does not come voluntarily.

It most often manifests in dreams, preceded by great emotion. Through magic, the doors of time and space are opened, showing a chaotic image of what has yet to come.

For years, Celestia's dreams have foretold her sister's wrath upon her return. For years, she has feared tomorrow.

But now, tomorrow may change.

Her dreams now tell of a chance, a hope that Luna might return to her by the same magic that imprisoned her so long ago.

Her dreams also say that Luna's salvation will come at the hands of others. Celestia has not trusted others for a very long time.

But in the morning, she prepares, she manipulates, she uses; all in the hope that prophecy might one day be reality.

It is hard for her to trust. But in the end, it is all she has.

Sun

The sun is brighter than she ever imagined.

When Luna returned, she came to Celestia first. Few words were said. Luna wanted revenge; Celestia accepted it.

She had never thought the sun to be so bright, so warm, so majestic.

So horrible.

Her plan is in motion. The Chosen Ones are on their way, searching for a power they already possess.

Celestia is well aware that they could very well fail. Luna might even kill them. Celestia would remain here forever, and she would welcome her fate.

Maybe then her heart would finally stop aching.

After

It was finally over.

After a thousand years, the Nightmare had returned. And thanks to the Chosen Ones, so had Luna.

Celestia knows she has no right to ask for forgiveness. What she had done to her was horrible. Despicable. Evil.

But she had spent a millennium waiting, trying to fill the hole Luna left in her heart with something, anything. But like square pegs in a circular hole, nothing would fill it.

Celestia asks, and for a moment, she is afraid.

Luna cries, and runs to her sister, and at long last, the Luna-shaped void is filled again.