"'To Miss Hermione Jean Granger, I leave my copy of The Tales of Beedle the Bard, in the hope that she will find it entertaining and instructive'…

Dumbledore left Hermione a first edition of The Tales of Beedle the Bard, a collection of wizarding fairy tales. One of those tales was about the three brothers who apparently met Death and received three objects that protected them from death. Inside the front cover was a symbol that led Hermione to want to visit Godric's Hollow, where she saw the symbol on the grave of Ignotus Peverell and where she and Harry were attacked by Nagini.

She leaned forward and held out The Tales of Beedle the Bard.“Look at that symbol,” she said, pointing to the top of a page. Above what Harry assumed was the title of the story (being unable to read runes, he could not be sure), there was a picture of what looked like a triangular eye, its pupil crossed with a vertical line. “I never took Ancient Runes, Hermione.”“I know that; but it isn’t a rune and it’s not in the syllabary, either. All along I thought it was a picture of an eye, but I don’t think it is! It’s been inked in, look, somebody’s drawn it there, it isn’t really part of the book. Think, have you ever seen it before?” “No . . . No, wait a moment.” Harry looked closer. “Isn’t it the same symbol Luna’s dad was wearing round his neck?”“Well, that’s what I thought too!” “Then it’s Grindelwald’s mark.”
Hermione later wanted to visit Xenophilius Lovegood, who had worn the symbol to the wedding of Bill Weasley and Fleur Delacour. At his home, Xenophilius told the trio about the Deathly Hallows, and they narrowly escaped an attempted ambush. All of these events led to Harry understanding the importance of the Elder Wand, which played a vital role in his final defeat of Lord Voldemort. Also, when Harry spoke to Dumbledore after allowing Voldemort to hit him with the Killing Curse, Dumbledore revealed that he had given the book to Hermione in hopes that the trio would figure out the Deathly Hallows, but only gradually, so as to keep their focus on destroying the Horcruxes and to prevent Harry from being too tempted by the Hallows, as Dumbledore himself was.