"Really? Was this the best you can do Harry?" The way Voldermort, no Riddle, because he was only a man, said his name made Harry's skin crawl with disgust. He thought back about how he got into this mess.
The young man stayed behind while his friends and prisoners of the Death Eaters made their escape from Malfoy Manor. Dobby, his brave friend, took the knife meant for him. After Harry saw the life leave the house elf's eyes, the world became a blur as he dodged, weaved and threw every spell he knew to against anything that moved.
Harry felt like he should be panicking. Spell fire flew all around him, a curse or two already hit him, but he refused to be on his knees for these wretches. A particularly nasty curse barely missed his head, though the blasting hex he sent back was rewarded in a shower of blood and gore.
Eventually, Riddle himself stopped everything with a wave of his wand, erasing all the spells in the area. Exhaustion and pain won out, and Harry collapsed onto one leg, the other laid out behind him torn apart and covered in festering wounds. He could not feel it, but it mattered little in the end. The important thing was his refusal to bow to these lesser ones.
Riddle strode forward, while his sniveling sycophants pulled back to allow their master room. "You certainly did better than I thought." The pale man looked around at the mayhem and brutality. "What would Dumbledore think of such merciless slaughter Harry?"
Even with curses and hexes wreaking havoc on his body, Harry spits out some blood at Riddle's feet while the man snarls at the disrespect. "Screw Dumbledore." Harry struggles to stand, despite the screaming pain in his mangled appendage that used to be a leg.
"I have seen the physical embodiment of destruction and death. Though I might die here, I go into death arms knowing that you will soon join me, for my goddess will not let you live any longer. There is no running," He paused. "So screw you Riddle." He hissed, partly in pain, mostly in hate.
"Oh Harry," Riddle tuts like a disapproving relative, before walking forward. "You sound like the madmen of France. I've looked into it you know." Harry tries to point his wand at the dark lord, only for him to wrench it free of his hand, physically overpowering the younger man with a flick of the wrist. "They all say the same. A creature, resistant, if not immune to magic and physical attacks. Over three stories tall, and weighing several hundred tons." Riddle circled the young man while he continued to speak, "All these stories about a massive monstrosity that hunger is so great that entire towns disappear overnight, with only debris left in its wake."
"There is no such being."
The manor quaked. The Death Eaters pause, along with Riddle. Then the manor shakes again, then again. Across the manor, vases and glasses shatter against the floor as the quakes became stronger, the pause between them becoming shorter.
Harry chuckles, a bit of madness in his eyes as he looks to the Death Eaters in front of him. "Do you feel that in your bones Riddle? For she is here."
The dark lord tried to point his wand at Harry, the tip glowing deathly green. The manor shuddered and the sound of wood and stone breaking outside of the room had the sycophants looking around in fear. With a shout of victory, Riddle casts killing curse at Harry. The distance between them left no way for the man to dodge, if he could. Wood snaps and breaks as the floor is breached by two massive horns goring the second floor. A massive maw stalagtite teeth covered in scales rises between Harry and Riddle, the deathly curse impacts it, only to be bounced back towards the dark lord. Riddle barely managed to dodge it. The manor crumbles around it, any death eaters that did not stand behind Riddle fell with the floor, only for the sounds of their bodies being crushed by debris and unseen feet. The creature finally made its free of the constraints that barely slowed it down.
With the manor crumbling to pieces around him, Riddle pointed his wand at the gargantuan creature in front of him, only to feel fear robbing him of his actions. The creature lunges forward, Riddle apparates away, while the unfortunate death eater behind him was not so lucky. The man disappears in a single bite down the monster's gullet.
The other Death Eaters see the master flee, while others die against the creature in front of them and take flight before the same happens to them.
As Malfoy Manor crumbles, Harry Potter watches from his patch of flooring balanced on the tarrasque's back. When the dust finally settles, Harry is gently lifted from the monster's back and onto the ground in the remains of the Malfoy's courtyard. The massive creature seemed to fight the urge to touch him, as if to check he was okay.
"I've just been cursed a few times mil'lady, I will be fine shortly."
The low rumble of growl came from the Tarrasque's throat, dislodging the human arm from between the creature's teeth as it flew off into the distance. It then shifts and shrinks, until it became human shaped. "Oh mon'cheri, what have they done to you?" Fleur flits about him, her wand flashing through numerous counterspells to stop any permanent damage.
"It matters not," Harry stated stubbornly. "Riddle thought himself better than you, and he needed to pay for it. You are greater than any mortal that walks this earth."
Fleur sighed dreamily. "You must be careful with your words, mi'amore. Those trash may sate my appetite, but I feel a different hunger growing."
"I will always be ready to serve you, my goddess, my monstrosity, my Fleur."