You mean Corruption
Static deafens his ears and dirt muddles his vision. Gray was currently on his hands and knees, reeling from a lethal blow dealt by his opponent. He had managed to defeat the dark mage, in exchange for some grave injuries and most of his magical reserves. He feels his arms and knees shaking. Gray could barely register anything, nor could he find any more vigor to fight. He would not be able to defend himself if someone attacked him at the moment.
He felt his consciousness slowly receding, that is until he hears his partner's scream.
Juvia had it worse for sure. Gray had battled the leader of the group but Juvia was left with around five generals to take care of. She had insisted on covering for him, after discovering that the head had an affinity for electricity, one that Juvia was certain to find difficulty in defeating.
Water was still a better conductor than ice.
Knowing that his opponent wouldn't be attacking anytime soon, Gray finds his eyes frantically searching for his partner. She looked dead on her feet, staggering from multiple cuts and bruises all over her body. She had discarded her heavy cloak to move more freely, revealing the angry red and black splotches that marred her skin. Her attacks where losing their aim as her enemy continued barraging her with dark magic, slowly gaining the upper hand.
Juvia managed to dodge a falling pillar, only to be caught unawares by her opponent. She registers a great stabbing pain on her lower torso, later on realizing what had impaled her. She gasped at the sight of a hardened and shiny steel knife sticking out of her flesh. She would've chosen to turn her body into water, if only she had the energy. She barely made a sound when the woman took a step towards her, pushing the knife further into her. She slid backwards and away from the weapon, catching a glance at the wicked smile on the woman's face.
She hears her name being called out, remembering that her beloved was still with her. Juvia falls on her side, ironically facing the victorious man who looked nothing but defeated.
Gray's mouth hung open in a silent scream.
Something dark stirs within him.
He takes time to watch her battered body shudder for breath. He sees the blood that she coughs out. Gray watches her shaking hands grip the large wound on her abdomen, sees the way she tries to muffle her screams of pain. He narrows his eyes when he sees Juvia attempt to stand. That would not be the best idea. She'd bleed to death before she would even manage to move a foot.
The enemy cackled with laughter, looking at them with as if they were insects beneath her boot.
Gray feels the familiar rage overtaking his body, sparked by the image of his lover dying before him. He removes his eyes away from her, knowing that he had seen enough. The sight is enough to make his heart race, his body tense and his eyes glint with murder. It is enough to change him.
Gray didn't scream nor curse. He didn't rush to her side or stand in front of her. That would mean weakness on his part. He wouldn't hesitate to do any of those things if he were the younger version of himself. But now that they had fought too many fights, partnered in so many battles, Gray knew better. Their opponent would surely use her to stop him.
Instead he gingerly rises to his feet, gritting his teeth in the process. His torn shirt falls uselessly to the ground, slowly revealing the beginnings of his corruption. He takes a step forward, almost buckling down to his knees again. He takes another. And another.
Gray marches forward, striding past Juvia's prone form. He knows her eyes are trained on him, guilty and fresh with tears. She knows what he is about to do. Juvia has seen him do it countless times for her sake. He hears him calling out his name, her voice pitiful and in pain. She sounded so helpless. He does not look back at her, shutting out her pleas. Her voice only urged him forward.
In fact, he wants her to pass out. He does not want her to see him like this, to see his body give in to darkness.
If Gray could not save her, then he would undoubtly do everything in his power to avenge her. Thus, he lets himself fall into a trance. He lets his body harden with resolve as he embraces the darkness creeping in his heart.
He sharpens his mind to a single goal. Unflinchingly zeroing in on the woman who pulled a dirty trick on his defenseless woman. She was still grinning widely, spouting nonsense at him and Juvia.
Something vile whispers in his ear.
It is something ugly and corrupt, violent and bloodthirsty. He acknowledges how sick it makes him feel, but he lets it out nonetheless. He cannot ignore the sudden burst of anger-no not anger- wrath that just wrecks his self-control and brings havoc to his senses. On any other day, he is merely a host for this thing, but today, he gladly merges with it.
Even if his body is worn out and his mind is muddled with thoughts of vengeance, there is always that sudden rush of adrenaline. A burst of energy. A source of strength.
It makes him forget the mission. It makes him forget that he is borrowing from evil itself. He forgets that he is not meant to kill. He forgets that this would burden Juvia's conscience for a very, very long time. It makes him blind to how the very woman he is trying to avenge, looks at him with sorrow and fear. Gray knows that she does not fear him, instead she fears for him.
Who knows what the consequences are for what he is about to do.
He could be arrested. He could be kicked out of the guild for breaking a law. His friends' perception of him might change.
Gray could care less.
It didn't matter to him at the moment. As long as he knows that he is doing this for his woman, allowing himself to succumb for her, he feared nothing. He'd do anything if it meant keeping Juvia by his side.
He'd died for her before, as she did for him.
He'd lived for her after the countless deaths of his loved ones.
And he would most certainly and without question, kill for her.
He does not want this power. He knows it is unclean. He knows it is strength borrowed from the devil himself.
But it is strength nonetheless. And it is what I need now.
He eyes the gruesome face of the woman who had hurt his partner, burning her with coal eyes. He does not even try to make threats or voice what he is about to do. The way he prowls and the way he stares are enough to tell the enemy that he is out for blood. He takes step after step towards the warry girl, knowing that she will be no more when he reaches her. He hears Juvia crying out to him, pleading with him to let it go.
She does not understand.
Gray knows the exact moment his eyes completely change by the way the woman in front of him gasps and starts to retreat. He can feel the darkness settle on his skin, the corruption covering his paleness. He welcomes the whispers of evil that always comes with it, listens to the prayers it chants in his ear.
He thanks the entity for giving him strength.
Thanks it for enabling him to avenge the woman who matters.