In an Alternate Universe

In another life, during the Giant War, Annabeth was stabbed.

Right in front of Percy.

And he couldn't do a thing. At night he got nightmares. They got bad, horrible even. His screams woke up most of the camp in the middle of the night, it terrified the younger campers.

And he'd wake up knowing Annabeth wasn't there to comfort him. That she'd never be there again.

Percy closed himself up. He stopped talking. He stopped coming out of his cabin, not even when Piper tried to Charmspeak him. His friends got worried. The gods got worried.

So in a last ditch effort, Chiron ordered a quest. A solo quest, for an extreme emergency. Percy would be going to school.

Not just any school, Hogwarts, A school of magic. But there was something They didn't tell Percy. A special add in from Aphrodite and Hades and Nico and even Thantos.

Percy was sorted into Hufflepuff, not that he really cared. The wizards were wary of him, even though Hectate blessed him with magic and knowledge, He wasn't an average acting person.

He'd spend his time not in class, roaming the halls miserably. No one tried to talk to him. No one tried to stop him.

But then a week after coming in he heard it. The twinkling laughter, that made his heart hurt. It sounded so much like Annabeth he couldn't stop himself from following it.

To the library. Behind the shelves. Where three curious students were standing among the books. A red head, A ginger, and of course, Harry Potter, who's face Percy would recognize even without the knowledge from every single poster in the wizarding world.

Closing right beside them was a glowing pale ghost, who was laughing.

Percy dropped his bag with a thud catching the fours attention. His mouth opened and closed like he wasn't sure what to do or say.

"Annabeth?" He choked out.

The ghost smiled, "Who else Seaweed Brain?"