A slow knock echoed against the chamber door.
"Enter," called Star Swirl the Bearded, looking up from his desk.
The door opened. Princess Celestia stepped inside and shut the door behind her.
"Hello, Star Swirl. I hope I'm not troubling you at this late hour," said Celestia.
"Of course not," said Star Swirl. He stood up from his desk chair and stepped around several piles of books and scrolls which lay haphazardly across the floor of his study. Then the old wizard gave a half-smile as he faced his guest and stroked his eponymous beard with a hoof. "Shall I pretend not to know why you're here?"
Celestia's neck stiffened. "You... already know?"
"It's my business to know things," he said, with a shrug. "Now let's get this silly admission over with."
Celestia took a deep breath, then stared down at her greaves. "Must I go through the motions if you already know what I did?" she asked, her voice barely above a whisper.
Star Swirl walked up to the princess and placed a hoof under her chin, lifting it up. Princess Celestia found the sensation unusual, given that nopony else in Equestria dared touch her.
"I think it will be important to our friendship," said Star Swirl, and he motioned Celestia to a small, empty table and chairs near the entryway of his otherwise-messy den.
The two friends sat. Star Swirl waited patiently for his protege to speak.
"I have violated your personal space in an unforgivable fashion," she finally said, her eyes shimmering wetly in the candlelight.
Star Swirl chuckled. "Unforgivable? Now that's an awfully strong word."
Celestia swallowed. "I scanned you while you slept, Star Swirl."
"I see," said Star Swirl. "And did your trespass into my innermost being slake your curiosity?"
The princess lowered her eyes to the table. "I still don't know what you are, but at least now I know what you aren't."
"I'm not a normal unicorn, you mean."
"That is an understatement," said Celestia.
"Come now, haven't you always thought I was special?" he asked, with a mock pout. "Don't hurt an old stallion's feelings. I have quite a reputation to maintain, even more so a millennium hence."
Princess Celestia looked up from the table and directly into her mentor's eyes. "Please don't make light of this. I know what I did was wrong, but I need you to understand why I did what I did," she said.
"I'm sure I already do, but it matters not. What's done is done."
"It matters to me," said Celestia, and she placed a hoof to her temple. "I simply cannot bear it any longer, Star Swirl. I must know how you can be so certain of your prophecy."
Star Swirl nodded slowly. "Ah. You don't trust me."
"I didn't say that," said Celestia. "I just don't know if your predictions will truly come to pass."
"Times are dark, my Princess. It is understandable that you should avoid taking anypony at their word, even me. You're no foal," he said. "The simple assurances of an old nag that some dusty prophecy shall be fulfilled far in the future were insufficient to persuade your troubled mind, so in a moment of weakness, you peeked into my heart. As far as I'm concerned, there is nothing to forgive."
"It's been almost three hundred years, Star Swirl. I feel so lost without her," said Celestia. "If I wait another seven centuries and she doesn't return... I can't bear to even consider it."
"I can imagine how you must feel, Celie," he said, and reached a hoof across the table to hold hers. "But your belief is not required. Luna shall return to you, just as I have foretold. You must try to be strong. I've gone to great lengths to ensure that all of these things shall come to pass—greater lengths than you can even imagine."
"Your abilities far outstrip my own," said Celestia. "I had always suspected you were more than you appeared to be. No single unicorn could ever have accomplished the feats you have."
"True."
"Is this why you haven't reached apotheosis?" asked Celestia.
"Essentially, yes. I cannot become an alicorn because the magic inside me is already too strong for any one pony to contain," said Star Swirl, as he teleported a tea set onto the table, complete with hot tea.
Celestia frowned as Star Swirl poured himself a cup of tea. "Scrying magic is inherently inaccurate. How can you be so sure of your predictions?"
"Tell me, Celie. Do you remember when I first met you?" asked Star Swirl, pouring a cup for his guest.
Celestia lifted the cup to her lips and sipped. "I do. I shall never forget it."
"True."
"Even though I was very young when it happened."
"False."
For a moment, a look of confusion crossed Celestia's delicate muzzle. "I don't understand. Is this another riddle?" she asked.
"I didn't say when you first met me. I asked if you remembered when I first met you. The answer to that is neigh," he said, then downed his entire cup of tea in one swig.
Celestia paused for a moment, then gasped. "The future. You mean you first meet me in the future, don't you?"
Star Swirl nodded. "This world is my distant past, but it is where I am needed."
"And you haven't even been born yet?" asked Celestia.
Star Swirl smiled. "Correct again, but in two separate ways. I wasn't born, I was created. And my time of creation is far in the future."
Celestia turned her head to the side. "Well, that... That is reassurance enough. After what I've done, I haven't the right to ask you anything further. I should go." She stood up to leave.
"Rights are overrated," said Star Swirl, rolling his eyes. He grabbed Celestia with his telekinesis and plunked her back into the chair. "Just this once, I will tell you what you wish to know, without any riddles or teasing. Just don't let it go to your head."
Princess Celestia adjusted herself back into her chair, took another sip of tea, and then set the cup to the side. "Who, and what, are you?"
Star Swirl smiled. "Do you ever wonder why I am so happy living alone, with few close associates?"
"Frequently," said Celestia. "I ache for my sister's presence daily. I cannot fathom what it must be like to be lonely by choice."
"I am not lonely," said Star Swirl. "I have a relationship."
"You're in a relationship with somepony?" said Celestia, her eyes widening with interest. "Why have you never introduced me to her—or him, or whatever?"
"No, my Princess. I'm not in a relationship. We are a relationship."
"Then the scan was true. You have two souls," whispered Celestia.
"Two complementary beings, swirled together," said Star Swirl. "One unicorn stallion of the rising sun, with incredible mental acuity but altogether lacking in magical talent. One unicorn mare of the evening light, blessed with overpowering magical talent but completely absent of discipline."
He gestured with his staff, and in the air appeared a very crude drawing of Sunburst and Starlight Glimmer. The two outlines merged to form a drawing of Star Swirl himself. "Together, as with any good relationship, we fill each other's gaps and become more than the mere sum of our parts. We are Star Swirl the Bearded."
Celestia paused for a moment to let the meaning soak in before responding. "Are you trapped like this?"
"Not precisely. We were together by necessity first, then later by choice," he explained. "This is who we are now. In the future, you shall get to know each of us separately shortly before your sister returns. Not long after her return, we too shall return to Equestria from Limbo and meet with our former halves. Their merging is further in the future still. When it happens, it shall send young Star Swirl far into the past while we remain in the future."
"You aren't scrying after all. You know the future because you've been there," said Princess Celestia, a soft smile returning to her muzzle. "You were born in the future, as those two mages!"
"Indeed," said Star Swirl, with a chuckle. "While the future is never set in stone, the prophesy is more than a simple prediction. With careful guidance, you shall see her again."
Princess Celestia breathed a deep sigh, and her ears drooped. "You say there's nothing to forgive, but I should have trusted you. If there's any way I can offer my penitence..."
Star Swirl stroked his beard in thought. "Perhaps there is a way. Princess, we beseech you to carefully remember this moment in the future," he said, his voice taking a somber tone. "Whenever you are faced with students who fail to live up to your expectations, even when they fail in spectacular fashion, do your best to remember the power and grace of forgiveness. Remember the guilt you are wrestling with now, and pay our kindness forward to those whom you take under your wing."
Celestia nodded solemnly and stood up again. Her back arched as though a great weight had fallen from her withers. "Then so I promise, old friend," she said.
"Good, and I have but one final request. To prevent paradox from arising, we shall lock some of our memories away prior to our confinement in Limbo. When we return to Equestria, we shall temporarily not remember who we were, even after we meet our halves," he said. "For safety sake, could you keep what you know a secret from us?"
"Most certainly," said Celestia, with a firm nod of her head.
A sly smile grew across Star Swirl's muzzle. "We must admit, paradox is not the only consideration. A return to innocence is a rare jewel to encounter, even in a life as long and storied as our own," he admitted, then winked at the Princess.
She smiled in return. "Then it shall be as you wish," said Princess Celestia. "Thank you, Star Swirl."
"You are most welcome. Now if you don't mind, we would like some time alone," Star Swirl asked, and Celestia left without saying another word.