The Collateral Realm is like if Harry Potter and The MCU had a baby, and that baby was raised by How To Train Your Dragon and babysat on the weekends by Lord of the Rings, who let it have playdates with The Owl House and Percy Jackson.
Nathan always loved the idea of falling into a magical realm and helping save the world, just like in all those movies, shows, and books. However, when it actually happens, it's not quite what he expected. Every move he makes only seems to endanger his new friends. And instead of stepping into the role of the 'chosen one,' he finds himself the final ingredient needed to destroy the Collateral Realm altogether. In order to survive—and maybe even get back home—Nathan must stop the True Spellcasters and their flawed vision to save the realm.