The scraping of the benches on the stone floor is obscenely loud as the Slytherin house collectively stands up and begins to file out of the Hall. The other houses are unusually still and quiet; the Gryffindors especially are uncharacteristically stony eyed. It is a sea of green and silver that leaves the Great Hall. Cowards; the word is not said, but ricochets around the mind of every teacher, student, ghost. Even McGonagall's face holds a hint of disgust. The teachers begin to call to the other houses to leave, for them to offer up their underage and unsure. In this chaos, it is not immediately noticed.
But it is soon evident that in the sea of silver and green, someone stops moving. Their friends jostle them, "Come on," is said to them, but they stand still as if their feet are glued to the ground. At the back at the line, someone else slows to a halt. Someone else looks uncertainly around at the Great Hall, runs their hand on the wood of the Slytherin table, and decides they can't bear to leave Hogwarts, their home, to be attacked. Slowly, they sit back down.
It isn't many. It's nothing, compared to the near army that sits at the Gryffindor table. But as the last person leaves the Great Hall, there are four people sitting at the Slytherin table. They look afraid; they look as if they'd have rather followed the rest of their house to Hogsmeade. But they are there, and they aren't leaving. The people remaining at the Ravenclaw, Hufflepuff, and Gryffindor table stare at them in surprise. This is not what they expected from the "bad" house, a house known for saving their own tails. This is not what they expected from the companions of Pansy Parkinson, who shouted "Grab him!" the moment You-know-who asked for Harry Potter. No one expected this at all.
It is quiet enough to hear a pin drop as one of the four remaining Slytherins gets shakily to her feet. She is small and blonde, but her gaze is unwavering as she stares down the Great Hall. Every eye is on her. Quietly, her hands go to her neck and she skillfully loosens her green and silver tie. A moment later, the tie is free and in her hand. She stretches her arm out and releases it, and it floats down to land on the worn wooden table. All is quiet for a moment. Then, another Slytherin stands up. His hands go to his neck, and then another green and silver tie is on the table. The other two Slytherins quickly follow suit, taking off their ties and discarding them. The four hold the breath and look at the other houses, an unformed question in their eyes.
At the complete other side of the Hall, a bench scrapes on the ground and someone stands up. The entire room watches, transfixed, as yet another tie, this one shining red and gold, lands on the table. As if on cue, the Gryffindor house collectively stands up and removes their ties. Soon, not only red and gold, but black and yellow and blue and bronze ties are falling, abandoned by their owners. The teachers are astonished; in all the days of Hogwarts, nothing like this has ever happened.
The last of the ties lands on the tables, and for once every student at Hogwarts is dressed identically. There is no more silence now; war whoops and excited chatter fills the air. Students climb over tables. Hands are extended to the Slytherins, beckoning them over. House boundaries that were once rules to live by are now forgotten.
Because tonight, Hogwarts is going to fight. And not as Slytherins, Ravenclaws, Hufflepuffs, or Gryffindors. They are going to fight as one.