Use of the locket

[smoky zinc]

I'm writing a hogwarts legacy fanfic and I'm at the gringotts area, but I can't remember what the locket was used for in the story. It didn't look like a locket imo it looked more like some kind of vial, but that's what it's called apparently. Does anyone remember the story use of it?

[midnight cradle]

The memory was in it

The one of Charles and Percival setting up the vault

But for future reference this isn't exactly the place for this sort of question

[scarlet meteor]

Yes. There's an inscription on the locket. If you read the inscription aloud, a map of Hogwarts appears out of thin air, showing traces of ancient magic near the Restricted Section.