
Not Actually Indie
Ok, maybe let's pool resources on who Amelia thinks the DP is.
I am betting that it's not someone who's in the original canon, and the reason they're not in the original canon is because the person is also Quirrell.
We've got a highly competent and accomplished person of Voldemort's generation, hailed as the second Dumbledore, who was considered a hero and fought against the Death Eaters. Who from canon fits that description? I don't think there's anybody, certainly nobody was ever mentioned who was considered a second Dumbledore. Adding a completely new and unforeshadowed hypercompetent original character to a fanfic is generally considered bad form, and would probably bother a lot of readers, so I figure any such character who seems to feature in the story is probably not simply a new character who's being shoehorned in, but a consequence of one of the original deviations from canon (note Eliezer's established history of doing this, from events like the deaths of Narcissa and Aberforth, to Hermione being sorted into Ravenclaw, not because she simply "fits better" there, but because the events of the story caused her to receive a bad impression of Gryffindor on the train ride to the school.) The most obvious way for a seemingly new hypercompetent character to be the result of the original deviations is for him to be either controlled by or another false identity of Voldemort, who already has an established propensity for creating multiple false identities. The competence of this character would then be a consequence of Voldemort's own competence.
If he was being Imperiused or polyjuiced or some other method of magical replacement, it would also explain his isolation and estrangement from his friends; Voldemort couldn't afford to be him all the time, and wouldn't want anyone around who'd spot incongruities between him and the original.
Also, if I were the Defense Professor and wanted a fallback secret identity, I'd want one where nobody would notice any niggling incongruities between me and my supposed identity, and one convenient way to accomplish that is if the other identity is also me.
edited 11th Apr '12 10:46:58 PM by Desertopa
...eventually, we will reach a maximum entropy state where nobody has their own socks or underwear, or knows who to ask to get them back.

I agree, he's only noted to be hypercompetent *after* his 25 year hiatus, when Voldie might already have been controlling him. In which case the only difference from canon would be Voldie not being stupid.
It is however true that Quirrel's age is not explicitly given, although it is hinted that he's closer to the Marauders' age than to that of Voldie or Dumbledore.
On the other hand I'd like to point out the conversation with Amelia: "I shall not name any names" Would she really say that to someone who she suspects pretends to be himself? I'd assign a low probability to that event, on account of Occam's Razor.
Finally, contrast these two quotes: "You will find nothing in the newspapers about Quirinus Quirrell until I decided it was time for me to teach Defense at Hogwarts."
and
"The young man took up his family's seat in the Wizengamot, becoming among the most steadfast voices against You-Know-Who. Several times he led forces against the Death Eaters, fighting with skillful tactics and extraordinary power. People began to speak of him as the next Dumbledore, it was thought that he might become Minister of Magic after the Dark Lord fell."
Edit: fixed oversight
edited 12th Apr '12 2:37:41 AM by Dirka

Amelia belives Quirrell is the scion from the war, and that he is disguising his appearance - Thus Quirrells apparant age is of no relevance what-so-ever. He doesnt look a thing like that scion would today, and she does not expect him to.

Has anyone else brought this up yet? This comes in chapter 3, "Comparing Reality to its Alternatives" just after Mc Gonagal has told young master Potter-Evans-Verres about the death of his parents. And that they had been hit by the Killing Curse and that he had survived it.
(And somewhere in the back of his mind was a small, small note of confusion, a sense of something wrong about that story; and it should have been a part of Harry's art to notice that tiny note, but he was distracted. For it is a sad rule that whenever you are most in need of your art as a rationalist, that is when you are most likely to forget it.)
Everything we believe is false.
edit.
I had a thought there that was rather alarming. What if instead of what I used to think was the case, that Riddle simply made Harry one of his Horcruxes, but swapped bodies with the infant?
edited 12th Apr '12 8:12:23 PM by TamH70
Mage of Life-Breath-Doom
Question: in what chapter Harry estimates the wizarding population?
"Here to welcome our new golden-eyed overlords," said Addy promptly.

Mage of Life-Breath-Doom
"Here to welcome our new golden-eyed overlords," said Addy promptly.

I am reading the book (again - I must be obsessed or something) so I will note when he does his rough estimate first and get back to you.
Shadowed Philosopher
I believe it's during his first trip with McGonagall, before arriving at Hogwarts. Or at least, during that trip he does some figuring regarding the likely paucity of scientifically educated wizards, which involves guesses as to the number of Muggle-borns who go to Hogwarts.
Shinigan (Naruto fanfic)

I was going to mention that as well, but he specifically mentions the comparison when he is thinking about which side he would be on in a final war between the Wizarding World and the Muggles. On the side of the six billion rather than the one million, and that is much later in the fic.
Shadowed Philosopher
I don't know if he actually mentions numbers there. My recollection is just that he compares them generically by size, then talks about the one reaching upward for the stars etc. and the other on a downward spiral.
Shinigan (Naruto fanfic)

He estimates Wizard population at about 1 million half way through Chapter 35 just after he finishes talking to Quirrel and is thinking that he would side with the Muggles against the wizards.

Why would Dumbledore let Quirrel teach at Hogwarts, if he knows he's not really Quirrel, but doesn't know his real identity? It looks like a big risk to take, with philosopher's stone and Harry in Hogwarts.
Shadowed Philosopher
Competent Defense professor. Say it repeatedly and loudly.
Shinigan (Naruto fanfic)

"Lily, take Harry and go! It's him!" shouted a man's voice. "Go! Run! I'll hold him off!"
And Harry couldn't help but think, in the empty depths of his dark side, how ridiculously overconfident James Potter had been. Hold off Lord Voldemort? With what?
Then the other voice spoke, high-pitched like the hiss of a teakettle, and it was like dry ice laid on Harry's every nerve, like a brand of metal cooled to liquid helium temperatures and laid on every part of him. And the voice said:
"Avadakedavra."
"Not Harry, not Harry, please not Harry!" screamed the woman's voice.
Whatever was left of Harry listened with all the light drained out of him, in the dead void of his heart, and wondered if she thought that Lord Voldemort would stop because she asked politely.
"Step aside, woman!" said the shrill voice of burning cold. "For you I am not come, only the boy."
"Not Harry! Please... have mercy... have mercy..."
Lily Potter, Harry thought, seemed not to understand what type of people became Dark Lords in the first place; and if this was the best strategy she could conceive to save her child's life, that was her final failure as a mother.
"I give you this rare chance to flee," said the shrill voice. "But I will not trouble myself to subdue you, and your death here will not save your child. Step aside, foolish woman, if you have any sense in you at all!"
"Not Harry, please no, take me, kill me instead!"
The empty thing that was Harry wondered if Lily Potter seriously imagined that Lord Voldemort would say yes, kill her, and then depart leaving her son unharmed.
"Very well," said the voice of death, now sounding coldly amused, "I accept the bargain. Yourself to die, and the child to live. Now drop your wand so that I can murder you."
There was a hideous silence.
Lord Voldemort began to laugh, horrible contemptuous laughter.
And then, at last, Lily Potter's voice shrieked in desperate hate, "Avada ke-"
The lethal voice finished first, the curse rapid and precise.
"Avadakedavra."
A blinding flare of green marked the end of Lily Potter.
And the boy in the crib saw it, the eyes, those two crimson eyes, seeming to glow bright red, to blaze like miniature suns, filling Harry's whole vision as they locked to his own -
some things to note:
Lily attempts to kill this individual
we don't see the man attempting to kill Harry.
These are the two major departures from canon. There's no reason to change these facts unless it's a clue/red herring.
It does sound like it's very possible that mort did not, in fact, try to kill Harry. It does bring up the question of why not.
Going off the idea that mort might have been both voldermort and our mystery former hero, it seems possible that he's trying the same con again. Remember that quirelmort was trying to get harry to agree to a mock victory over voldermort (just after the stanford prison experiment chapters.)
3016 storyyeller13th Apr 2012 10:32:01 PM from Appleloosa
, Relationship Status: RelationshipOutOfBoundsException: 1

More like giant cherries
Would it be possible for Quirrelmort to posses Harry once he becomes an accepted leader of the Wizards? Or depending on how good people's detection spells are, he could posses Harry as soon as he leaves Hogwarts (where the takeover would presumably be detected by the wards).
edited 13th Apr '12 10:32:56 PM by storyyeller

canon!mort could possess people, it didn't work out so well though...
HPMOR!mort is rather intelligent though, if there's a way to do it he'd find it.

Sage of Stories
edited 14th Apr '12 5:33:16 PM by Shinzen
3019 storyyeller14th Apr 2012 07:36:44 PM from Appleloosa
, Relationship Status: RelationshipOutOfBoundsException: 1

More like giant cherries
I don't really remember what happened that well. So Dumbledore thinks things happened like in canon, but the dementation vision showed that Lilly tried to kill Voldemort?

Sage of Stories
edited 14th Apr '12 8:52:51 PM by Shinzen
Somewhat Anomalous
But, as i have said before, why would Genre Savvy Voldemort go to the trouble of trying to kill/possess/Memory-Charm/Legilimise baby Harry when he could just have a few dozen Disillusioned Death Eaters quietly surround the place and raze it to the ground? Then he could have gone in personally to ensure nobody survived, and wiped Godric's Hollow from the map with Fiendfyre.
I think you'll find it's a bit more complicated than that.

Maybe it was an assignment he wanted to do without the DE finding out?
"You should always go to other people's funerals; otherwise, they won't come to yours." Yogi Berra.

Sage of Stories
edited 15th Apr '12 8:39:09 AM by Shinzen

Dealing with the baby in person is the Genre Savvy way to do it (it's even in the Evil Overlord List!), unless you've actually read Harry Potter. The only other case I can think of where the herobaby is dangerous is Hercules, who killed the snakes sent to kill him in the cradle.

Imagine if the movies had gone the Disney route and had Harry sing a Power Metal ballad about how he can go the distance...
... Note that Hercules' scene in Hades is very HPJEV-ish...
"You should always go to other people's funerals; otherwise, they won't come to yours." Yogi Berra.