Equestria had already been stunned by the return of Nightmare Moon — learning that one character of myth and legend was real, was the sister of Celestia herself, proved a powerful blow to the nation. Their princess was in a period of mourning after the re-banishment of her sister, and uncertainty crept across the land.

When the Crystal Empire returned, bringing with it living shadows and mind-controlled armies, that shock was compounded twofold.

But shock gave way to determination. Princess Celestia rose from her grief. The ponies of Equestria rallied. Peaceful ways of life had to give way to sacrifice for the good of the nation.

At first, there was concern among the alicornis imitato; where could they serve? A few felt capable of joining the call for volunteer fighters, but found themselves rejected. Too handicapped magically. Too great a distraction. Too high a personal risk if they were targeted for their alicorn appearance; too great a chance the few with cult followings would accidentally cause dissension and disobedience in the ranks.

Then Celestia called them in. Each one of the twelve, and their families, escorted to the castle in Canterlot under guard. For their safety, she assured them. They would bear no suspicion, they would not be harmed, and their loved ones were welcome to the same protection unless they wished to help the cause in some other capacity. And the AIs trusted her, for hadn’t Princess Celestia always made an effort to get to know each AI, to befriend them, to demonstrate to them her friendship and wish for their good?

None were aware of the ulterior motive behind this special consideration. True, keeping them safe, keeping them under a watchful eye, was a wise tactical move. But in truth, Princess Celestia had need of something else they had power over — power none of them realized was theirs:

The Guardians.

With each AI safely protected in the castle, the Guardians were now available. Twelve of the most skilled, elite agents in Her Royal Service. Twelve ponies picked for their patience, their decision-making, their stealth, and their fighting skills. Twelve ponies who had proven themselves not only strong and capable, but compassionate and rational — ponies with the rare skillset required for competently watching over, protecting — and, if need be, stopping — another pony in secret, for decades on end. And never once be found out, or require gratitude, for their service.

She had a special mission for them, if they agreed. They did. And so the Guardians gathered, trusting their charges, their foremost responsibility, to the Princess’s care.

There had been a Crystal Heart once, she told them in the secret meeting chamber. The Crystal Ponies had once powered and protected their city with its strong enchantment — an enchantment fueled by their love for one another. It had been a beacon of hope and light, a physical manifestation of the King’s love for his creatures. And Sombra had stolen it from them, filling the void left behind with his malice and lust for power.

He could not have broken it, she was certain. It must be hidden in the castle. And if they could find it… reactivate it… free the crystal ponies from their enslavement… the war would end, and no more innocent lives, lives utterly overshadowed by Sombra’s wicked hubris or laid down to defend Equestria’s freedom, would be lost.

The plan might not work. It might be too dangerous. It might be a fool’s errand.

But there was no group of ponies, Celestia felt sure, who could be more well entrusted to such a task.