The Virelli Twins and the Dead Horizon

Elowen and Seraphina Virelli, heterochromatic‐eyed twin witches from Hogwarts, accidentally tear open a rift in time and space during a forbidden spell, landing themselves-and a handful of familiar magical friends including Harry, Hermione, Neville, Luna, Draco, Fred, George, Viktor Krum, and Andromeda Tonks-inside the world of The Walking Dead on the very night Rick Grimes is shot.
Together with Rick, Glenn, Maggie, Michonne, Carol, Daryl, Abraham, Rosita, Ezekiel, Shiva, Connie, Magna, Yumiko and other survivors, they race to save Rick's life with healing charms, then uncover Lori and Shane's secret affair. Fusing magic with muggle ingenuity, they transform an abandoned prison into a fortress of hope-planting enchanted crops, warding the walls with runes, and booby-trapping cells with Fred and George's prank-inspired defenses.
When grotesque new aether-walker hybrids-creatures fused with temporal magic and glowing runes-emerge from the woods, the alliance is tested in a brutal moonlit battle. Drawing on ancient protective charms, Durmstrang dueling jinxes, and the unbreakable bond forged between both worlds, they drive back the undead threat. As dawn breaks over the blood-stained courtyard, the twins pledge to trace the hybrids' origins in the legendary vault of Aetherhall-and to master the dangerous magic that brought them here before that power consumes everything they've fought to protect.