Goldfinger + male protagonist Cedric + time travel + partial magic modification
When Cassandra, a librarian from another world, fell into Hogwarts with a rune notebook in her arms, she thought it was a life stream of "catching up ancient books" - but it turned out to be a life stream of "carrying fragments to hide from Voldemort".
Can the light rune she unlocked protect against dementors? By the way, turn Boggart into Snape in a lace skirt; want to paddle in the Triwizard Tournament? The fragment forced her to be a warrior, and she had to give Harry a protective rune. At the scene where the Horcrux was destroyed, someone waved a wand and she took out the pendant: "Can this fragment melt the Horcrux? If not, I will add a buffing rune."
During the interview after the war at Hogwarts, the Death Eaters cried and reported: "That woman took a notebook and put a golden light on it, and shouted, 'The rune combo is cooled down'!"
The Ministry of Magic jointly stated: "This Death Eater is so controlled by the Imperius Curse that he can't even distinguish between 'runes' and 'crazy words'. Do not believe it."
Cassandra closed the note: "Today is also a day to protect the peace of the magic world in the way of a librarian~"
There is also my number in the storybook
Purpose: Using "librarian's knowledge and otherworldly runes" as weapons, in the crisis of Hogwarts, use a relaxed and playful way to break through the darkness and protect tenderness and survival.