Either explain it or don’t.
When authors include things that don’t fit within the real world–magic, time travel, anachronisms–there is an impulse to explain how it works. Which can be fantastic for worldbuilding, but if you don’t know what you’re talking about, it can make more problems than it solves.
Stephenie Meyer tried to explain some bizarre thing about chromosomes, and it made the biology of vampires and werewolves make no sense. Suspending disbelief worked better in that case before she tried to ground it in the real world.
Lemony Snicket, on the other hand, just has random anachronisms that are never explained, but because there’s nothing even close to resembling an attempt at an explanation, we can just shrug and go, okay, that’s how it works. The magic in Harry Potter seems to basically not be grounded in anything, but we can believe it within the context of the story because she doesn’t try to ground it in anything.
In Jim Butcher’s Codex Alera, on the other hand, he goes into a lot of magic theory, and it gives us a strong feeling of worldbuilding. There’s enough logically coherent explanation for it to feel grounded within itself.
It is possible to go too far (see: Orson Scott Card’s Xenocide and Children of the Mind) where the plot ends up so tied in the reader understanding intricately detailed scientific and pseudo-scientific minutiae that the story is incomprehensible without it.
Generally, though, if you’re going to make something up, either say it exists and leave it at that, or entirely figure out how it works. Halfway is always less believable than nothing at all.
#I have sometimes heard this distinction referred to as ‘hard’ vs ‘soft’ magic #by analogy with hard vs soft sci-fi #in hard sci-fi you spend an entire chapter explaining how dyson spheres work #in soft sci-fi spock does some technobabble and then suddenly reveals that vulcans have extra eyelids #similarly hard magic is when harry potter knows 10 spells with very specific effects #and soft magic is when gandalf appears and shines some weird light in the sky that drives the nazgûl away #I think hard magic is useful for having characters overcome obstacles in interesting ways #because we (the readers) get to see how the pieces work and then how they’re used to solve problems #whereas having the main characters solve problems with soft magic feels like a cop out #like if frodo suddenly revealed that hobbits have extra eyelids that can melt cursed gold #and just straight-up wrecked the ring right then and there #but soft magic is fine if the obstacles aren’t the main focus of the story #e.g. star trek TOS is more about the crew and the scenarios than it is about the science #so it’s still a good story even if the actual conflict resolution was largely technobabble #and I think it’s also really useful for conveying a sense of how big and complex a world is #like we learn a lot of specific things that hermione harry and ron can do #which is hard magic #but we also see dumbledore and voldemort dueling using things we know nothing about #which is soft magic and serves to underline how much the kids don’t understand #similarly frodo’s magic sword and lembas bread are hard magic #because they have well-defined rules for how they work #but gandalf running around doing crazy things underscores how much bigger the world is than frodo will ever be able to know #and thus gives the world a sense of enormity that it wouldn’t have if we understood all the magic in it #tag rants #sort of #magic (sufficientlylargen)