I am writing in between the sixth and seventh book. Hence, it can not be disproved until the next book comes out. Even when it does come out, if this theory does not match the novel, it is because Rowling is wrong… not me. I am perfect! I don't make mistakes. J.K. Rowling hinted at this throughout the last two books, and if she doesn't use this… she isn't the brilliant author, (well at least story-teller,) that we think she is. BTW, if in fact it is proven correct in the seventh book… you all owe me five dollars… Except for you. You're O.K.!
Many years ago;
"Expelliarmus!" Albus felt, more than saw the red lightening bolt whiz by his ear, landing ten feet in front of him, and throwing up a cloud of dirt. He stopped running, turned toward his countless pursuers and thought of Minerva.
"Expecto Patronum," he cried with all of his might, as a blue Phoenix shot out of the tip of his wand and hit the nearest of the attackers square in the face, knocking him into the others. Cries of pain, confusion, and "Protego", bounced off the gray stone walls, following him in his race.
He kept moving, praying that he wasn't too late; praying more that he was even going the right way. Two guards loomed up ahead; definitely the right way. A weasely-looking wizard shouted for him to stop as his broad-shouldered companion, barely fitting into his loose robe, reached into his pocket. Dumbledore didn't even stop, he just raised his wand, ignoring the incantations they sent bouncing off the walls, and muttered "Incarcerous".
Ropes crept out of the floorboards and engulfed the guards, like a large carnivorous vine. Before they even dropped their wands, Dumbledore was past them, forcing the heavy metal door open with "Alohomora". What the young professor saw before him, grayed his hair instantly and finally made him stop short.
Two silhouettes were standing over a dying man…Tellius. Rage burned inside of him as the door swung closed behind him, and none but the third man turned to look. A smile spread across his face, and then fell, as did his entire limp body. Gritting his teeth, Albus heard footsteps behind him, coming down the corridor, and scrambling over the fallen guards. Before he could conjure the spell, a hissing voice did it for him. "Colloportus" The door sealed behind him, as he himself was about to do. The footsteps crashed into the unmoving door, and continued to bash against it in frustration. The Death Eaters would have to wait for their meal until their master was done with him. They were scavengers anyway.
Looking around, Albus soaked in the room. It was straight out of a medieval torture chamber, with a burning torch chandelier in the center of the high rise ceiling. Directly below the flaming monstrosity, the hooded figures turned.
Dumbledore could make out their faces clearly now, and as expected he was staring into the dead eyes of his world-renowned ex-student. "Tom, stop this foolishness. Let Tellius Malfoy be the last victim of this war."
Tom Riddle turned away, and produced his wand, while his loathsome companion spoke. "Albus, why do you fight us?" Though relatively young, he had the raspy voice of a dying cancer patient. Spending time with the Dark Lord aged you quicker than a strong 'maturing incantation.' That's why the average lifespan of a Death Eater was three months. (That and the constant threat of Aurors, and even your own master, simultaneously.) "You know your side is weak. This world is in need of justice, and Tom…"
He was cut off by a livid Riddle. "What did you call me Aldous Black? What did you say you abhorrent worm of a man?"
"Lord… Master. I beseech you. Please forgive me." Kneeling, Black kissed Riddle's black ring, grimacing at the metallic, dead taste. Although it tasted like the blood he craved and lusted for, his thirst was unquenchable.
Aldous was Tom's newest servant. He was a lackey out to "destroy the mudbloods" and do 'God's work', or something. They all knew it was bullshit. To them, Tom was God. Soon, Black would be thrown away as a private servant, either to perish or join the Death Eater's growing ranks. But for now, as second in command, he was as much of a bodyguard as someone with Tom's immense power needed. Basically, he was a pet dog, out to bite the hand that fed him, when, (and if), he could.
Turning back to the body of Dumbledore's fallen comrade, Riddle shouted "Serpensortia". Nagini, Voldemort's most loyal snake, leapt from the tip of his wand. He cooed to it in that disgusting Parseltongue language, and it approached the corpse. For a split second it looked as though she was going to consume the body, engulfing the dead eyes of Dumbledore's friend and switching it for her own yellowing reptile eyes. Albus quickly tuned his gaze away in anticipated disgust.
"Valentendio Horcruxio." Before Dumbledore could stop it, Voldemort, Tellius, and Negini were all drenched in an eerie blue glow, coming from within them all. Half of a neon green translucent snake slithered from Riddle's chest; while a half of a red see-through serpent crawled from Tellius's dead lips. Floating in mid-air, they joined, and in a single motion, jumped into the body of Nagini.
It all took a fraction of a second, but standing there, transfixed at the spectacle, Dumbledore gaped. "You can't make an animal a Horcrux!"
Smiling slyly, Lord Voldemort turned to face him. He looked a little paler, and very weak. "If I thought we might meet again, I wouldn't have shown you how wrong you were about that. However, seeing as you only have a few moments left on this Earth," he raised his wand, pointing it into Dumbledore's face, "I thought I'd give you a nice farewell present. Nagini… Attack!"
Albus's half moon-spectacles snapped as he twirled his head around. Concentrating on Riddle's words, he had not seen the snake come up behind him. Nagini opened her mouth wide and leapt at the young wizard. A moment before his face could be ripped to shreds, Albus screamed, "Avis". A flock of birds shot from his wand, Fawkes among them, and tore at Nagini's scaly skin, hindering her attack.
"No, protect the snake Aldous!"
Black looked flustered, not sure if he should aim his wand at Dumbledore or the birds. Aggravated, as if to say 'it's hard to find good help these day', Lord Voldemort screamed, "Accio snake!"
"Nigini flew across the room toward the now hunched over Tom Riddle, and an instant later, they were gone in a puff of green smoke."
"It's just you and me now, professor." A sneer fell across Black's face, as he lunged with his wand. "Avada Kedavra!"
"Protego!"
The green light smashed into Dumbledore's magic barrier before bouncing away, back toward the attacker.
Aldous remained standing for a second, the sneer still pinned to his still face. He seemed to float there for an eternity, before his swaying legs and flailing arms dropped him to the ground, where he lay still, on top of Dumbledore's greatest friend. (He knew Tellius's son loathed him, and would blame him for the death, but that didn't matter now.) His worst enemy's servant lay atop his best friend in a dead heap at the center of the room, and Dumbledore broke down. He cried for the loss of his beloved friend, for all those suffering at the hands of the Death Eaters, and mostly over his loss of innocence. This was the first person, wizard or otherwise, that he had ever actually killed, (even as in this case, accidentally.) Black had underestimated Dumbledore's power. He was one of the few wizards, (Riddle included), strong enough to counter a killing curse.
The pounds on the door ceased suddenly; replaced with screams, and bugles playing the Auror anthem. The cavalry had arrived. A dragon roared behind the door and smoke sizzled through he cracks, making Dumbledore's eyes water. Growls and snarls of mythical beasts from both sides sounded, and he screams escalated. Wiping tears out of the corner of his eyes, (tears completely unrelated to the billowing smoke still spilling into the room), Dumbledore buried his head in his hands, and gently rocked back and forth while the screaming outside the door finally stopped. A victorious roar sounded from the Auror captain, Loriann Munchers, and was echoed throughout the hall by his team.
Rising on shaky limbs, Albus stared down at the dead Death Eater before him. Then glanced over at Fawkes, still flapping his wings and levitating at the professor's side; and his eyes fell back on the body.
"On an animal? I wonder…" Raising his wand, Dumbledore prayed this would one day be of use to him.