Work Text:
The one with the power to vanquish the Dark Lord approaches...
Born to those who have thrice defied him, born as the seventh month dies...
And the Dark Lord will mark him as his equal, but he will have power the Dark Lord knows not...
And either must die at the hand of the other for neither can live while the other survives...
The one with the power to vanquish the Dark Lord will be born as the seventh month dies...
1. There is no timeline
It could be talking about a Dark Lord at any time after the prophecy was made (b/c it says will be born, not was born). It could be talking about the Dark Lord they think it is talking about, but a baby born in a future year. It could even be talking about the child they think it is talking about, but a different Dark Lord!
2. There is no location
There is no reason to think it is talking about a British Dark Lord, or a European Dark Lord, or even a Magical Dark Lord. It could be literally anyone that uses or could be called 'Dark Lord.' Also, they obviously only looked for babies in Magical Britain born at the end of July. Why would they think it had to be a child born to magical parents, or even in Britain?
3. What does born to those who have thrice defied him mean?
Thrice defied him for the parents could be in the loosest sense possible. It could even refer to the son of the descendants of the ones who defied him. Born to those who defied him does not necessarily mean born to the people who specifically stood against him. It could mean born of the family of someone who has defied him, which could mean a lot of people, including any of the people involved with Voldemort's raising in the orphanage, or a similar situation for whatever Dark Lord it turns out to be about.
4. Who is the other?
The interpretation they come up with in the books, where it refers to 'each other,' might be the case… but it could totally be talking about a third party. For all we know, it could be a prophecy about the Dark Lord and the one with the power to vanquish him teaming up against whoever 'the other' is!
5. With the power...
does not mean with the desire to! There is no way of knowing if this means there will be someone born who will defeat the Dark Lord, or if it means there will be someone born with equal or greater power to the Dark Lord who will team up with the Dark Lord, or never meet the Dark Lord, or whatever!
6. As the seventh month dies...
What seventh month? They obviously decided it meant the seventh month of the calendar they used, but it could mean the seventh month after the prophecy was told, or the seventh month of literally any other mainstream calendar, or the seventh month of a calendar that is no longer in use, or even the seventh month of a different planet! It could conceivably mean literally any time, ever.
7. Either must die at the hand of the other for neither can live while the other survives
As discussed above, the other could be a third party. Also, even if it does mean each other, living and surviving are very different. It could mean that as long as one of them is only surviving, neither of them can truly live. It could also mean that they are literally incapable of dying except at each other's (or the other's) hand. It also could mean that whatever the worst state of one of the pair is, the other will have to endure, too, so if one of them is surviving rather than living, both of them are… and if one of them dies, both of them do. Obviously not a very desirable outcome for the Dark Lord.
8. What does vanquish mean?
If you look it up in the dictionary, you'll get various things, from totally annihilate to defeat in a verbal spar. It could basically mean any sort of defeat.