And before someone say "rip-off" or "IP violation" - let's check the borders of the copyright laws to make sure we do nothing wrong. Most of the following discussion will come up to 2 terms: "public domain" and "generic".

Public domain generally refers to something so old, it's no longer subject to copyright limitations. The specific cut-off dates differ from country to country, but mostly you are looking at everything released before 1930s as already safe for being used. The most well-known example in escape room industry is "Sherlock Holmes" - the 19th century story, which anyone can base it's escape room on (as long as you don't pretend to be the actual author of "Sherlock Holmes").

This availability, however, does not transfer to specific later creations based on public domain IP. Simply speaking - you can use Sherlock Holmes, but you can't use Downey Jr or Cumberbatch in their Sherlock Holmes impersonation. You can use Thor, as he's the god of thunder from nordic myths, "released" quite a while ago. But you can't use the specific looks of Thor from Marvel universe or Chris Hemsworth images. These newest creations are called "derivative works" and are subject of their own copyright expiration countdown.

"Generic" is a word, describing something as wide and unspecific, that it can't be copyrighted. Though some people see any magic-themed escape room as "Harry Potter" rip-off, you obviously can't copyright things like "magic", "superpowers" etc.

"Game of Thones" and "Harry Potter" will never appear unless "Lord of the Rings" and "The Lion, the Witch and the Wardrobe" had paved the way years before. And "Lord of the Rings" in all it's beauty will never appear without medieval myths and epos. The success of certain stories is determined not only by their gifted authors (which is obviously important, too), but also by the demand for certain stories and themes, circularly appearing in society over the decades.

Usage of specific titles, personal and location names (like "Harry Potter" or "Hogwarts") is always a bad idea. But magic itself is not a property of Joan Rowling or Warner Bros. - it's a generic concept, which can and should be used.

The upcoming Netflix "Witcher" series are about to become "the next best thing" and thus, most probably, a new battlefield for some of the copyright holywars. And while is heavily relying on books and less on the video game series, "Witcher" has not appeared from nowhere - it's set on a rich foundation of slavic myths and epos. The specific story is unique and belongs to it's authors in fullest, while the setting, the lore and the general appearance are all generic and based on centuries-old and "public domain" materials.