Before The Storm
He's calm as he grips the Blade. All around him chaos waits to rain down in blood and destruction, but within his mind it's calm. All else has cleared. Fear and doubt has fled to leave only purposeful clarity, and there's only one need burning within him that he needs to satisfy:
Kill.
His fingers flex on the handle of the weapon. Blood beats hot beneath his skin and pounds in his skull as he feels power flooding every inch of his body. There's something inside of him, some dark and violent part that the Blade calls to, drowning out every other thought with the bloodlust singing in his veins. Dean isn't sure how long it's been there. Maybe Hell put it there. Maybe it's been there all along. But something deep inside his soul cries out for destruction and pain and rejoices as he delivers it.
The Blade descends, ripping through flesh without resistance and then rising to slash down again. His job is already done. Abaddon is dead, but there's still a part of him that's thirsty for more. The Blade is his and now there's no power in the universe that can stop him.
It's crazed and bloody as he continues to stab down without thought or hesitation, but he barely notices the mess or registers that he should stop. Dean sits in the eye of the storm. It's calm like the ocean, still and tranquil far from shore, but he'll still drown in it as the dead weight drags him under.
The Blade feels heavy in his hand. He feels its power pumping through his veins, full of strength and vitality, yet still its a burden. But like the weight of guilt that sits in his heart, it feels like it belongs. The bloodlust gives him purpose to fill the empty space inside him, and he's grateful for it. The Blade is part of him, the bone an extension to his own skeleton, giving him another set of jaws and teeth with which to maul and tear and destroy. He uses it now, not stopping until he's ripped the corpse beneath him to shreds and devoured every inch of it, because the bloodthirst won't be slaked.
He feels it as he slips under the surface, so that he loses awareness of everything but himself and the thing he's so intent to destroy, but he doesn't care. Drowning only hurts at first, when the first inhale burns the lungs and tears at his insides, but he already passed that point with Magnus. Now he's ready to give himself over to the Blade's power completely, and he loses himself in the euphoria of destroying the empty vessel beneath him as completely as he can. It feels less like dying and more like pure elation.
Dean doesn't know how long he's been lost for when Sam's voice finally breaches the surface, but when it does, it's enough to pull him out of the darkened pit he's sinking into. He finds himself gasping for air as he's dragged forcefully back above the water, breaking its surface of calm equilibrium. Around him blood lies thick upon the ground, coating his arms and face and clothes, and the Blade falls from his hands as he's confronted with what he's done.
It almost feels like the spell is broken as the physical connection is severed, the bloodlust abating to give way to a kind of shocked exhaustion, but he knows it isn't over. There's still something gnawing away inside him, calling out to feel the Blade in his hand again and hungry for more, and sooner or later he's going to give it what he wants.
All this time he's been standing on the brink, not quite falling into the tempest of violence that the Blade awakens in him, but there's no denying his true nature for much longer. It was Hell that first revealed it: the broken part of him that craved blood and revelled in dealing out pain, and Purgatory summoned it back to the surface again for a short while. Now the First Blade is slowly stripping away everything that hides it, and although Dean can still feel resistance within himself, he knows that a storm is coming.