One of my favorite phrases my Creative Writing professor had for when you’re writing fantasy is ‘giving your story a Flux Capacitor’.
Because it’s not real, it doesn’t exist. But the way it’s thrown into Back to the Future, at no point does it throw the audience off or suspend any more disbelief than time travel would. You believe Doc when he says he created the Flux Capacitor - the thing that makes time travel possible, because the universe never questions him.
So it essentially means like, there are going to be elements to your universe that are just not gonna make any sense, even if you set up a whole system based on it. And the only way to make it work is completely own it. You cannot second-guess your system or else the reader will too. You can give it the strangest explanation, but write it like you own it.