what would the dewey decimal classification for fictional magic systems be? would it just be magic (fictional concept) in general or is there smth more specific that covers like magic as concerns worldbuilding?
Magic as in parapsychology and the occult would be under 133
Magic as in tricks and illusions would be under 793.8
Magic systems as used in fiction for worldbuilding would be classified under whatever category you're looking at it from; if you are designing a tabletop rpg/adventure game, it would be under 793.93. For video games, 794.8. For novels, it would probably be in the 808.3 under literature/rhetoric of fiction. A lot of worldbuilding guides I could find are not classified in the Dewey Decimal System, so they might not be considered non-fiction. Maybe look in the reference section?