Magical Merpeople

Explanation

Harry and Hermione felt as if they were guests in their own bodies.

After Dolohov threw his signature curse at them and taken Cleo to use as a shield, something inside of them snapped. The scum of the earth had dared try to harm her and they wouldn't allow it.

The moment they had sunk beneath the waves, they immediately had pushed him into deeper waters until he let Cleo go in favor of trying to attack them only to freeze when he realized Harry and Hermione had started to change before his eyes.

Their eye sight was enhanced immensely, they felt their bodies were different. Everything about them was different but they didn't care. No, their focus was solely on the Death Eater before them. When he lifted his wand, Hermione moved forward and was past him, her arm outstretched and a gurgle shout came from the man behind her.

They circled him, making sure to not let him escape and they notice his wand arm was bent, his wand having been ripped away from his hand. Leaving him defenseless.

It felt almost natural. Primal even. Surrounding this man...their prey. They snarled at him, realizing that even their teeth had changed into sharp rows of fangs. They knew what they were doing was not right, they should knock him unconscious and drag him back to shore. But a bigger part of them was solely focused on eliminating the threat. Permanently.

The moment he turned, was the moment he made his last mistake.

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Harry and Hermione floated in place, snarling and watching what remained of the man sink. They turned to one another before something catches Harry's attention from the corner of his eye and quickly turns to it, not having calmed down yet.

Hermione does the same and see five figures close to their size and a smaller one some meters away.

Tilting their heads a bit, they slowly swim towards them. All the while assessing if they were a threat. They both came to a stop a few feet from the mermaids. The little figure swam forward, causing the mermaids and the odd looking male among them to try and stop him, only to be stop by the odd looking female mermaid with them.

Harry stared as the young one swam to him and gave him a smile. Suddenly both Harry and Hermione calmed down and realized who was in front of them before looking down at themselves.

Whereas Hermione racked her brain as to how and why her body looked the way it did, Harry was reminded of the merepeople in the Black Lake he had encountered during the Second Task and how alike he looked like them. Bringing up their hands, the noticed they're webbed and their nails have been replaced by razor sharp like claws. Turning to the other they also see their eyes look more like a predators than a humans.

A small hand on Harry's cheek brought him to the little boy, to Teddy. Said boy was smiling at him as his eyes took in the shape and color of Harry's. For his part, Harry brought him for a hug and closed his eyes in tranquility. Teddy then pushed away from Harry and went to Hermione, giving her a hug as well. Finally, Teddy swims back to Andromeda and the duo take in the looks given to them by the resident mermaids and Lewis, whom looked close to collapsing.

Figuring the cat was out of the bag, Harry motioned for them to swim to the surface, figuring the girls had been underwater close to their limit of fifteen minute. They hesitated for a moment before slowly doing so after Hermione went first. Lewis was about to follow only to be stopped by both Andromeda and Harry.

He opened his mouth to say something but only bubbled gurgles were heard. Harry then motioned to the area behind his ears while looking at Lewis. Confused, he did the same and felt something that wasn't there before and turned to Andromeda. Understanding what he needed, she moved her hair and Lewis could see that, behind her ear, she had gills.