The Monster's First Arrival!
“Expecto Patronum!”
As Harry shouts out this spell from the bottom of his soul, a bright light comes from the tip of his wand, bolting out to take the form of a pale stag before ramming into the cloaked Dementors before him and his currently catatonic cousin.
As the Dementors were driven away, Harry panted a bit heavily. After all, it had been a hot minute since he'd had to use a decent portion of his magic like that. Harry quickly realized something though.
His Patronus was still there, and still ready to protect.
That meant there was another threat around similar to the Dementors, or maybe just more of them. Harry let the stag stay out as an odd looking man walked over. Something wasn't right though. The man felt off. His eyes were too wide apart, his mouth a little too far to the left.
“Are you alright there?” The man attempted to ask before the glowing buck charged the man, throwing him back. The man's form became even less human, his skin becoming a sickly yellow, and there appeared to be small puncture wounds where the stag’s antlers had pierced the man, no, the monster’s flesh, drawing what Harry assumed was the creature's blood, but it wasn't quite right. It ran too thick, and too bright to be blood.
“Honestly, such annoying little things!” The man exclaimed as one of his arms lengthened to a horrific degree, not quite stretching as much as it was loosening, the skin appearing to be crinkled like paper before it flared out to a length of almost two meters, and the fingers fused together into an odd, bone-white blade-like formation that dragged along the ground. His other arm seemed to also shrink, like the size had been taken from it to make the other the way it was.
It then moved forward and swung its arm-blade at Harry’s Patronus, the blade cutting into it, and Harry suddenly felt a large amount of pain. Looking down for a moment, he saw blood. This time, it was his own as it came from a wound on his shoulder.
Quickly, he ordered his Patronus to knock the creature away before either of them could get hurt any more. It managed it, but only barely, and still ended up getting a small cut to the side, showing up on Harry as well.
As the creature was stunned, Harry tried casting a body bind on the thing, but when the spell hit, it simply fizzled into nothing, making the creature chuckle.
“Aww, such a cute attempt~ I'm going to enjoy this~!’
After saying that, the creature charged at Harry, too fast for his Patronus to do anything. Harry saw his life flash before his eyes. He felt a tear come to his eye as he realized he'd never see his friends again, even if they hadn't tried to message him. He would never get to return to his home. He would never get to grow old, or find new love! He wasn't even an adult yet! Unfortunately, Harry couldn't think of a solution. The spells he knew seemed like they might just be useless, and even the Patronus was risky, nor would he have time to dismiss it and recast it before the thing could reach him. The blade arm was raised in the air as the creature got closer, intent on taking Harry’s life. Before this could happen though, a chain with a blade on the end of it pierced through the thing’s chest, splashing Harry with the creature’s blood as barbs bursted out of it to keep it from moving further as it was dragged back.
At the other end of the chain, Harry saw an old looking man who was grinning as he pulled on the chain, dragging the creature back. When the creature turned in mid air, getting ready to swing at the man to remove his bald head, Harry got scared for the one who had just saved his life.
That fear, fortunately, was misplaced, as the man grabbed more of the chain, and blocked the hit from the blade as it swung at him before kneeling the creature in the gun. He then moved behind it, pulling the chain further through before stabbing the thing through the back of its head. When the blade sunk in, the creature became more monstrous, barely even humanoid at that point, before fading to dust.
The old man sighed, and the chain disappeared as he moved over to the two boys, pulling out a wand. “Are you boys alright?”
Harry and Dudley were both too shocked to speak fro a moment, just nodding a bit. Harry managed to regain his composure first as the man began waving his wand in a motion he was more familiar with than he'd care to admit: the medical diagnostic spell. The old man began muttering under his breath, with Harry managing to figure out a few things he was saying like, “...showed up again” “...but why here?” “...need to heal them” “...prepare them for it.”
“W-wait, who are you, and how did you kill that thing?!” Harry exclaimed, flinching as he was reminded of his wounds, with Dudley getting bolstered by Harry’s ability to actually function after the situation.
“Yeah, a-and what was that thing?!”
The old man sighed as he pulled out a bag Harry hadn't noticed and handed him a vial with a purple liquid in it. He also handed Dudley a vial with an orange colored liquid in it.
“Drink those, then I'll answer.”
The two boys seemed skeptical, but Harry drank it down, hoping he was right to assume it wasn't something to keep him from fighting back or something. The potion tasted terrible, as he expected, and he gagged on it a bit.
He was right to assume, and his wounds began to mend themselves, bolstered by some spells Harry didn't recognize, which seemed to help him heal faster. He also felt the aftereffects of the ordeal begin to fade as well.
Seeing the wounds on his cousin heal, Dudley quickly drank his down, gagging much harder than Harry had, much less experienced with the… acquired flavors that potions tend to have.
He then felt himself grow a bit stronger, and felt the aftereffects of the evening begin to fade away as well.
The two of them sighed before looking at the man expectantly as Dudley spoke up, having a new wave of confidence after feeling the effects of the potion.
“You said you would answer our questions if we drank those gross things, and we did. Now spill!”
The old man chuckled a bit. “Ah, the energy of youth. Alright, I did say I would do so. I'll do it in reverse order though.”
He turned to Dudley. “That thing was called a cognatus, or relative. It looks human, and can mimic humans, but it can never get it fully right. This led humans to develop a way of telling when they were interacting with them so they could get away from them.”
Then, he turned to Harry. “As for how I did it, I used soul magic to manifest my own as a weapon. After all, they're similar to Dementors in that the best way to fight them is with the thing that they lack: a soul.”
His grin started looking a bit more like one the twins would wear when a prank they'd spent who knows how long setting up goes well. “As for my name, I'm Gellert Grindelwald. So, would you like me to teach you how to fight this time things?”