How Do You Make Cultures So Vibrant?

Dig deep rather than go wide. Having one or two cultures that play off of each other in an interesting way — where you’ve considered a lot of the ramifications — are going to be better than trying to create 30 different cultures. Try to keep focused on what’s going to be important to the characters and the books, and try to spend your worldbuilding there. So like if the characters are going to have conflict over religion, spend time on religion. But if instead they’re going to have different linguistics and that’s a source of conflict, spend time on the linguistics.