Disclaimer: Harry Potter and its characters, locations and anything else does not belong to me.
Warning: High canon material usage, though slightly (very slightly) worded differently.
A/N: So, this was just a small what-if thing I had on my mind a year back, and looking back on this, I decided to polish it a bit and post it. I'm pretty sure better writers have already discussed this incident, but I wanted to try my own hand at it. Enjoy!
What If – The Resurrection Ritual
"B-blood of the enemy... Forcibly taken... You will... Resurrect your foe."
There was nothing Harry could do. Wormtail knew how to tie ropes well; Harry was struggling hopelessly, unable to move. Squinting, he saw the silver dagger held in Wormtail's remaining hand.
'Forcibly taken... forcibly taken... forcibly...' Suddenly he had an epiphany. He had no idea whether it would work or not, but he had to try.
'Take my blood, Voldemort. I freely give it to you for your resurrection,' he thought, stopping himself from struggling against his bonds. He calmed down, and then tried to mutter the same words he thought over and over again, but it was very difficult to do so thanks to the black material Peter Pettigrew had roughly put in his mouth.
'I want to give Voldemort my blood,' Harry thought, but deep inside he felt afraid. He seriously didn't want to give his blood to a megalomaniac just like that.
'Nobody said anything about giving it because I sympathize with Voldemort or something. So I'll assure myself that it's because I want to see him defeated,' he tried to reason. 'Take my blood because then you won't win. I give you my blood so that you can finally go die like you should have the last two times.' He rephrased.
This could be the only chance he would get to disrupt Voldemort's ritual.
Honestly, Harry had been getting tired of how doggedly the Dark Lord had been pursuing him. His whole life had the shadow of Voldemort cast over it, and he had been hailed for living, made into a celebrity because the man had killed his parents but failed to kill him.
Harry had always wanted a normal life, but it was as if he had jumped from the frying pan into the fire regarding that wish. Not that he didn't like his new life, but it was as if his two best friends and a place where he felt like he belonged came at the price of him facing death year after year. And it was wearing him down.
The black-haired teen was brought back to reality as he felt the point of the knife penetrate the crook of his right arm. As the blood seeped, Wormtail took a glass vial from his pocket. Harry tried to ignore the pulsating pain in his arm, instead concentrating on what the rat was doing. The vial was held to his cut, and drops of blood fell into it. Wormtail staggered back to the cauldron and poured Harry's blood into it.
The liquid within instantly turned coal-black and bubbles started to escape, making loud sounds as they broke. The potion looked almost angry, if liquids had expressions.
Wormtail was surprised. The book had said it was supposed to turn white with shimmering diamond sparkles, but he couldn't think very clearly due to the sharp pain, and he dropped beside the cauldron, sobbing due to the pain.
'Please let it have drowned,' Harry thought. 'Please let whatever I did have worked.' Harry fervently prayed, hoping somebody out there would hear his wishes. He had a bad case of luck over the years, he seriously hoped it would turn around now and the Powers That Be would hear his wishes. And they were granted as the evil Voldemort baby fell out of the cauldron, huge burns on him.
"Potter," it rasped, "I will be back. You cannot stop me," it said before falling silent.
'Cliché.' Harry blinked. 'Did he die?'
Wormtail faintly raised his head, looking at the mutilated corpse-like body of his master.
Harry knew he needed to escape from here, find a way back to Hogwarts so that he could inform the Headmaster of everything that happened. Though he couldn't see any way that Voldemort could come back, he knew better than to underestimate the Dark Lord. In case Voldemort kept his promise, they would all have to be prepared.
Thinking of a way with which he could escape his bonds, he remembered what Dumbledore had told him at the end of his third year.
"Pettigrew owes his life to you. You have sent Voldemort a deputy who is in your debt. When one wizard saves another, it creates a certain bond between them... and I'm much mistaken if Voldemort wants his servant in the debt of Harry Potter."
"I don't want a bond with Pettigrew!" he had replied angrily. "He betrayed my parents!"
"This is magic at its deepest, its most impenetrable, Harry. But trust me... the time may come when you will be very glad you saved Pettigrew's life."
'That time is now,' Harry steeled himself. 'Or should be.'
'I don't know how to call in a debt,' Harry thought. 'But well, I learn things better through experience, don't I?'
"Peter Pettigrew, I call in the debt you owe me for saving your life," Harry intoned, spitting out the black material, and started coughing immediately afterwards. He had tried to make his words sound all formal and archaic, although he really had no idea whether you could even ask for the debt.
He was promptly surprised as a white light encircled him and Pettigrew.
"I accept," Peter, the coward, said. He was shaking in fear. The white light became more pronounced, and the two of them had to close their eyes as the light blinded them before turning into a glow.
Harry knew from one of the books that Hermione had read to him, about the tournament and the contract, that a contract and a debt are pretty much the same. If you don't fulfill it, you either lose your magic, in the best case, or die, in the worst.
"I ask of you to remove my bonds and set me free," Harry said. He hated all this formality, but what could he really do about it? If this magic was as deep as Dumbledore had said, then it would probably require him to speak like a Malfoy (he could already imagine Malfoy talking all stiff and formal and calling in debts to his father left and right).
Pettigrew came and untied the ropes as Nagini slithered around Harry. Harry got the feeling that it was only this light that was keeping him alive from a vicious bite from Nagini.
Now the light reached its maximum, blasting outward. As Harry opened his eyes, he saw that he was the only one awake. Pettigrew was down, due to the huge snake now on his chest. Both seemed to be unconscious. The only person left would have been Voldemort, had he not already fell.
Now he needed an escape plan.
A/N: I know the debt was non-compliable with canon, but take it that it works like that only when you call upon it, or otherwise it'll just fulfil itself in whatever way possible. I hope this seemed plausible enough – the phrasing of the ritual seems vague enough for this to happen.
Edit (07/04/17): Cancelled the Horcrux-destroying properties of the debt.