Author's Note: This is an Alternate Universe story set in the Unbroken Universe. It is third in a trilogy consisting of Promises Unbroken and Promises Remembered.

Disclaimer: I do not own the characters or settings of Harry Potter, but the concept and creation of the Unbroken Universe are mine. I simply thank J.K. Rowling for being so kind to those of use who like to play in her sandbox.

Promises Defended

One Choice.

One Chance.

One End.

Prologue: Promises Deferred

October 10, 1992

Somehow, he supposed that it had to be this way. Maybe, just maybe, there had been no avoiding this outcome, no way to avoid this aspect of his many choices. Or perhaps he simply had to run away.

And it was too late. He had to get away, fade into the shadows, before he lost himself completely. The process had already begun—with every breath of air he sucked in, he could feel the darkness' influence growing. And every time he exhaled, it felt like losing a part of himself.

No more. Standing alone in a darkened room, he had spoken the words aloud, had somehow sealed his fate with them. No matter that there had been no one to listen. No matter that he had been alone—and no surprise, that. No more. He would draw the line. He would fight back. He would end this frightful process, one way or another. No longer would he be a pawn in the hands of darkness—or even in the hands of fate. He didn't believe in fate, and he would fight back. Even if he had to break his heart to do it.

Surprisingly steady hands had gathered all he would need: the research materials, the journal, and his wand. Then he had closed the door behind him, leaving the others to find what he left behind—very little, in the grand scheme of things: a taint of Dark Magic, a few handwritten notes of no consequence, a slightly charred robe damaged through a bit of juvenile carelessness, an upended stool, and a trio of empty cauldrons. There were no clues, no story of where he had gone. There was simply emptiness.

He had not returned to his quarters in the Main Villa; there was nothing in the Old Suite that he could not do without. Instead, he had headed west of the lab and almost to the island's shore, feeling something building within him the entire way. Was that sorrow? It was impossible to tell. Somehow, he had become distanced from his emotions, distanced from his humanity. He could, however, feel the emptiness. It grew with every moment, even when speaking to a man who Sirius knew he should not have treated so coldly. Even when James had tried to reach out, the emptiness refused to fade.

And so he left. Before he could drag them down, before he could force his friends to watch him become the monster they so feared. He left as another had before, in secret and in silence, knowing not when he would return or even if it would matter. He was consciously following in another's footsteps, praying that he might find a different road within the darkness and knowing that the odds proclaimed he would not. But he had to. There was no other way.

The doors to SecApp opened for him without protest, almost as if the island was glad to be rid of him. The Isle of Light did not take kindly to the presence of a creature who should have felt at home upon her darker twin, located less than twenty miles to the north and eager to embrace him. Dark and light—linked islands that would have symbolized their conflict if only the world remembered enough to recognize their significance. But he did not travel to the darker twin, welcome though he would have been. Instead, Sirius fled before the part of him that ached for that darkness could take over. He would not give in.

He would not accept.

"And still the offer remains."

The words echoed in his ears, three hundred and six days later.

"Remember that."

He remembered. How could any sane man forget?

Except he wasn't sane. Not really, and not anymore. Not yet. Sirius shivered, from what he now realized was not external cold. The cause was the darkness within him, the cold hands that gripped him. Hands he had no way to escape—save one. This one.

So he fled Avalon, speaking to no one, and leaving no evidence of where he was headed. In truth, he did not know himself—he had no way to know. He could only run away from everything he held dear in hopes of saving it. Of saving himself.

Even as he Disapparated, he knew it was wrong.