Lucius Malfoy bowed as he presented his Lord a sphere of glass — the odd container that the Unspeakables had created for Prophecies. Good. Any other news? Potter had escaped? Ah. Unfortunate. But with the Prophecy in his hand, it ought not to be too hard to catch him again. A word of disdainful congratulation, and Malfoy was sent away. Voldemort, almost smiling at the thought of his approaching success, said a word, an ancient word he had weaseled out of Slughorn all those years ago (not with any special purpose — just because it would never hurt to know such obscure lore) to hear a prophecy without destroying it; and the recording of Sybill Trelawney's First Prophecy began to play.
The one with the power to vanquish the Dark Lord approaches...
Yes, he had heard that part before. That had seemed reassuring: the boy had the power to vanquish him, but nothing said that he inescapably would do so. So far, so good, as they said.
Born to those who have thrice defied him, born as the seventh month dies...
Yes, yes. Ah, why could these things never be straightforward? It couldn't have hurt to just say it would be the son of the Potters? When he became God-Emperor of the Earth, he would have to look into forcing Seers to be clearer from now on. He'd lost precious time figuring out who had thrice defied him and was going to have a son.
And the Dark Lord will mark him as his equal, but he will have power the Dark Lord knows not...
How was giving the boy a scar marking him as his "equal"? That hadn't even been intentional. As for the power he knew not, that was only expected. A half-blood Hogwarts student couldn't possibly have more raw magical power than the Dark Lord; whatever the difference in their power arsenal was, it had to be knowledge of a specific kind of spell. Even more reassuringly, the present tense Trelawney had used technically only said that he didn't know this power at the time. He still had the opportunity to learn it before his showdown with the boy. Now, to the part he had longed to know all these years…
And either must die at the hand of the other, for neither can live while the other survives...
Oh. Now it was not mere possibility; it was fact that the prophecy was referring to. So… according to this, either he would have to kill the boy, or the boy would kill him. It was no longer a matter of power; this prophecy thought it could play men like puppets — that they would have no choice but obey its whims. Killing the boy had been an important goal of his, but that could not go on for a minute longer, if it had not truly been his will, if his moves had been dictated by whatever alien creature crafted Prophecies to confuse men. Lord Voldemort obeyed no one, Lord Voldemort only ever acted on his own volition. Ah, he could see it, now, what the Prophecy intended to happen… It counted on him doing all he could to kill the boy, sinking all his time and resources in this impossible task, until he would be left so vulnerable that the boy succeeded. A perfect happy ending for Dumbledore, no doubt.
Well, Lord Voldemort wouldn't be the toy of Fate. So he wouldn't kill the boy; did this suffice? No. The boy would still try to kill him, even if he was not directly targeted… for the sake of his friends, of the world, of Dumbledore's ideals of Peace and Good. The Prophecy would aid him in that task, no doubt. But Fate wouldn't, couldn't win. Voldemort's mind raced to find a way to circumvent the Prophecy at every possible turn. Turning the boy to his side? No, that couldn't be done. He was a Gryffindor if there ever was one. A Dementor's Kiss, perhaps? It would leave the boy alive, but with no soul left to think about killing him. No, too dangerous as well. That too, the Prophecy had foreseen. Trying either of those things would inevitably fail and only strengthen the boy in his determination to fight him as hard as he could.
Then he saw it.
There was only one possible option. The boy's plans couldn't be changed… or at least, not by his own actions. But his own plans, he could call off.
No becoming God-Emperor of the World. No more Death Eaters, no more war. No more murders. That was the sacrifice it would take to make the boy's side stop fighting. They wouldn't be happy with the arrangement; no doubt that they'd think justice had to be served, that even if he no longer killed, Tom Riddle should stand trial. But he'd give them an ultimatum, under veritaserum. Either they would also vow not to harm him in any way, and he would disband the Death Eaters and retire in some remote place as a magical researcher; or they would refuse, and the war would start again, more terrible than ever. In this event, of course, the Prophecy would ensure that he wouldn't win, but hundreds would die before Fate got the better of him.
He had torn apart his very soul to live forever. Giving up a planet was no less extreme, and he would make that sacrifice as well.
"Severus! I need you to carry a message to Dumbledore for me."