I just came across an amusing term, Potterdammerung, for the end of the Harry Potter phenomenon.
For those who don’t follow German opera based on Norse mythology, the Götterdämmerung was the Twilight of the Gods — and the last of Wagner’s four Ring-saga operas:
The title is a translation into German of the Old Norse phrase Ragnarök, which in Norse mythology refers to a prophesied war of the gods which brings about the end of the world. However, as with the rest of the Ring, Wagner’s account of this apocalypse diverges significantly from his Old Norse sources.The term Götterdämmerung is occasionally used in English, referring to a disastrous conclusion of events.