Harry Potter was spending Christmas at Hogwarts, like every single other holiday, because naturally, the Dursleys would never take him. He stared out the window into the snowy courtyard, lost in thought, when suddenly he saw something odd. There was a black patch of space appearing in the midst of the snowy Hogwarts courtyard, like someone had spilt black ink on pure white paper. As Harry stared, the black spot grew bigger and bigger until it became doorway-sized, and out stepped the strangest people Harry had ever seen.

There was a boy around Harry's age, with spiky dark hair forming bangs over his striking cerulean eyes and wearing a strange black costume, festooned with brightly colored buckles and zips all over the place. He was followed by some strange creatures Harry had never seen before, not even in his Defence Against the Dark Arts classes. The first looked like a giant white duck, but wearing a strange blue costume resembling a sailor's uniform and wielding a strange looking staff, while the other was a somewhat canine looking creature with a green shirt and yellow pants, holding a shield. As soon as the trio appeared in the snow, they immediately drew together, forming a tightknit group with their backs to each other, eyes warily scanning the Hogwarts courtyard.

Harry leaned in closer to the window, wondering at the strange behaviour of these strangers, when suddenly the courtyard erupted in with strange black creatures that almost looked like mini Dementors. Harry gave a cry of surprise, but the strangers appeared to be expecting this, and began fighting them with strange weapons: a staff, a shield and a strange sword in the shape of a key. It took Harry milliseconds to figure out what he had to do. He quickly grabbed his wand and rushed out of Gryffindor tower, making for the courtyard.

Harry left Gryffindor Tower and made his way out of the Fat Lady's portrait and quickly down the castle towards the entrance. He ran lightly down the empty hallways and was going down the stairs when-

"Ooof"

Harry bumped into someone as he was rushing down the stairs towards the Hogwarts courtyard. Looking down, he saw Luna Lovegood sprawled out on the stone landing, her blonde hair in disarray.

"I'm sorry Luna, I was just in a hurry and-"

"That's fine Harry." Luna got up and dusted herself off. "Is it the nargles?"

"What? No, no..."

Luna turned to go, then suddenly Harry had a brainwave.

"Wait, Luna. It's not nargles, but it's definitely not something I've seen before. Get your wand out too. You'll need your DA training for this. Follow me to the courtyard."

Luna nodded her head, her radish earrings swaying wildly under her hair. She got her wand out from its holster and followed Harry down to the courtyard.

The strange boy was there, and there seemed to be more of the strange black creatures. Harry heard Luna gasp behind him. Turning to look at her, he saw that her eyes were alight with a strange enthusiasm he'd never seen from her.

"Heartless!" Luna said. "Quick, call your Patronus!"

Harry had no time to think, and instead just shouted "Expecto patronum!"

He saw the familiar silver light come from his wand, with the silvery spectral stag chasing the black figures away from the strangers and destroying them.

And it looked like they'd reached there not a moment too soon.