What if...

Dogs and Dragons

Harry opened the door hurriedly at the end of the dimly lit corridor with the alohamora charm. Filch was on their tail. Harry, Hermione and Neville shut the door quietly but quickly as they all sighed in relief, Hermione clutching Harry's hand to her chest tightly.

That was, until they heard a low growl from behind them.

They turned around to see a gigantic three-headed dog snarling at them.

Hermione and Neville screamed as Harry looked up in awe.

"Oh, this was the thing you showed me in the library, Hermione! What was it, a Cerb-" He started excitedly.
"LESS TALKING MORE RUNNING!" Neville yelled while the Cerberus looked in confusion at the strange trio. Neville bolted the door shut just as Harry made it out. They sighed in relief yet again.

"You- you remembered it. I'm impressed." Hermione panted. Harry just gave a mischievous smirk back.
"Are we forgetting the GIANT THREE HEADED DOG IN THE-" Neville yelled, visibly paling. Harry whipped a hand over his mouth.

"Filch might still be near." Harry warned.

He wasn't. As they made their way to Gryffindor tower, not once did they run into the scary caretaker.

They entered the common room hurriedly, finding a massive party in celebration of Gryffindor winning the quidditch match.

"Ah, if it isn't the man of the hour!" Fred announced loudly.
"We have been anxiously waiting your arrival, oh esteemed ruler of these lands." George exaggerated, mock bowing and gesturing to the punch table.

"You two are brilliant." Harry looked around, grinning.

"My lord-" Fred bowed.
"You flatter us." George followed. Hermione giggled quietly as Neville ran straight to the punch bowl. Harry looked over to her and shrugged, then followed Neville. Hermione shook her head and joined them.

Then, Ron chucked a glass of punch straight at Harry.

Harry caught it.
"Thanks." He smirked, before downing it. Ron's gormless expression was priceless.
"Lucky catch." He grumbled. Hermione walked up to him and slapped him as hard as she could muster.

"You don't touch him, Ronald Weasley, or I swear I will rearrange your DNA structure so you turn into a pig, because that's what you are!" Hermione yelled at him. Everyone had went quiet. Ron was glaring at Hermione with all the death he could muster. Harry stared at her in admiration, then shook his head and got some more punch.
"Truly brilliant." He muttered. Hermione must have heard, because she smiled down at her shoes like they were made of pure gold.

As Harry, Hermione and Neville found a quiet corner of the common room, they started discussing the near-death experience they had just encountered.

"Did you both see what it was standing on?" Hermione said excitedly.
"I was too busy looking at the h-heads." Neville shuddered.
"It looked so confused when I acted cool in front of it." Harry boasted.
"Harry, you are never going to be cool." Hermione facepalmed. Harry faked hurt, then grinned as he turned back to Neville.
"He's really sweet, though." Hermione thought as she smiled to herself, then mentally slapped herself and forced herself to get a grip on the situation.

"It was standing on a trapdoor. That means that the Cerberus is guarding whatever Hagrid took from Gringotts!" Hermione explained.
"Cool!" They both said at the same time. Hermione rolled her eyes.

"So what's the dog guarding?" Harry asked Hermione.
"I'm not sure." Hermione suddenly pulled a book out of absolutely nowhere and had a brief read. "It could be anything! An extremely powerful wand, a magical bomb, a-" Hermione continued listing items.