As soon as Voldemort got into the cauldron, changes began happening to his body.
"Finally!" he thought, he was going to be reborn again after having spent the last fourteen years as a shell, less than the meanest ghost. Thanks to the Horcruxes, his spirit was bound to the physical world, keeping him alive. He had waited for so long, and at last, it was happening.
His previous attempt when he latched onto Quirrell was unsuccessful and he went back to the forest in Albania.
Only after he met Wormtail did they together build a rudimentary body that Voldemort used for travel and performing magic. While in this form, Voldemort was forced to drink a Rudimentary body potion made from unicorn blood and venom from Nagini, a snake he befriended, to sustain his life. Voldemort also chose to make Nagini the last Horcrux he created.
Upon torturing Bertha Jorkins, a Ministry of Magic worker, Voldemort learned about the Triwizard Tournament and the survival of one of his loyal Death Eaters, Bartemius Crouch Jr.
Voldemort made all the plans to manipulate the event of the tournament leading to this moment. Yet, now that he was finally in the process of regaining his body, there was another obstacle in his path.
Inside the cauldron, Voldemort felt the presence of an intruder. An unfamiliar soul was trying to fit it.
"Did that fool Wormtail mess up with the ritual?" Voldemort thought for a second. But Voldemort knew that was not possible as he monitored the whole preparation. This was not something that was supposed to happen. The two souls circled each other and collided against each other.
Outside, unaware of what his master was going through inside the cauldron, Wormtail began speaking. The trembling in his voice was clear as he seemed frightened beyond his wits.
He raised his wand, closed his eyes, and spoke to the night.
"Bone of the father, unknowingly given, you will renew your son!"
The surface of the grave at Harry's feet cracked. Horrified, Harry watched as a human bone rose into the air at Wormtail's command and fell softly into the cauldron.
The cauldron's magic pulsed, amplifying the struggle between Valor and Voldemort. It became a battle of wills.
Valor understood that the current Voldemort was in a weak position. He was in the middle of a ritual, had broken his soul so many times to create the Horcruxes, and spent so long without a body; all these things must affect Voldemort.
Valor pressed on. He did not know exactly what to do, but he felt the need to collide with the other soul. He put everything in each strike, trying to weaken Voldemort's hold on the rebirth process.
Sadly, everything was new to him. Compared to the dark Lord Voldemort, who had experience manipulating the soul, Valor was a nobody in such a matter.
Back in the graveyard, Wormtail pulled a long, thin, shining silver dagger from inside his cloak.
His voice broke into petrified sobs.
"Flesh ... of the servant ... w-willingly given ... you will ... revive ... your master."
Wormtail extended his right hand, holding the dagger firmly in his left. With a tight grip, he swung the dagger upward. Harry anticipated Wormtail's actions a moment before they unfolded, and he shut his eyes tightly. But he couldn't escape the piercing scream that cut through the night. The sound alone was enough for Harry to imagine Wormtail cutting his own hand. Then a sound echoed as something hit the ground, followed by Wormtail's labored breathing.
Harry opened his eyes for a split second and saw Wormtail's hand on the ground. Then, a loud splash marked the dropping of something into the cauldron, indicating Wormtail throwing his hand into the cauldron.
The potion now glowed with a fiery red hue. Voldemort recognized that Wormtail had completed two steps, leaving only one. Time was of the essence; failure to act swiftly would result in unimaginable consequences. The other soul would be taking his body instead.
How humiliating would it be for him!
For the final step, Wormtail approached Harry.
"B-blood of the enemy ... forcibly taken ... you will . . resurrect your foe."
Harry, tightly bound, was powerless to prevent it. Squinting down, he struggled futilely against the ropes strangling him, observing the silver dagger trembling in Wormtail's remaining hand. The dagger's point found its mark in the crook of Harry's right arm, and he felt blood dripping down the sleeve of his torn robes. Wormtail, still panting from the pain, fumbled in his pocket for a glass vial and positioned it beneath Harry's cut, allowing the blood to fall into it.
Wormtail staggered back to the cauldron and turned the glass vial, causing the collected Harry's blood to fall inside. Instantaneously, the liquid transformed into a blinding white. The cauldron was bubbling, sending its diamond sparks in all directions, so blindingly bright that it turned all else to blackness.
As soon as Harry's blood fell on the liquid, Voldemort used everything possible to destroy the invading soul.
And then, suddenly, the sparks coming out from the cauldron were extinguished. Voldemort was successful in eliminating the invading soul, the one belonging to Valor.
Before the story of Valor even began, it had already ended.
Yet, it was not a complete victory for Voldemort. He felt something different after his last collision against the soul. But he did not have time to ponder on it as the ritual was at its utmost stage.
A surge of white steam rose thickly from the cauldron instead, obliterating everything in front of Harry, so much that he couldn't see Wormtail or Cedric or anything but vapor hanging in the air.
But then, through the mist in front of him, he saw, with an icy surge of terror, the dark outline of a man, tall and skeletally thin, rising slowly from inside the cauldron.
Its face was whiter than a skull, with wide, livid scarlet eyes and a nose that was flat as a snake with slits for nostrils. He was clad in dark, flowing robes that seemed to dance with shadows as Voldemort moved away from the cauldron.
Just as he was about to examine his own body, Voldemort's mind was flooded with a searing headache that felt as though a torrent of memories was cascading into his mind.