Let’s talk magic and religion. They are not always symbiotic. Is it that way on your world? How does the magic work? Do you need ingredients to cast a spell or just a word? Are there more difficult rituals that must take a longer time to perform?What are the limits for your magic? How many spells can you use before you’re “empty”? (Make sure you take into account the difference of using many simple spells up to more than one difficult spell.)How does one gain magic power? Do they gain it from a higher power, by reading and learning from books, from genetics, or some other way? (You can always gain help with this area from D&D player’s handbooks.) Are there forbidden spells or forbidden paths of magic? Some good examples of what is usually seen as a forbidden path or magic are necromancy and blood magic, or Demonology/pact magic. For the higher level spells, why are they more difficult? What about them makes them more difficult? The amount of magical power or prowess needed? The necessary ingredients? The time period needed to cast the spell?Is magic illegal in your world? Would your character(s) need to hide that they have magic? If it’s illegal, what happened to make it illegal? What are the main religious beliefs on your world? Is one more recognized than the others? Why?

Religion is a big part of every culture that can influence the daily life of large groups of people so it’s important to define it if present in your world. The other thing is that is a good way for world building, you can define the life of people, the way cities are built and the way of thinking of the population.-

Polytheist or monotheist: choose the type of religion that fits best in your world, it’s important because polytheist and monotheist religions have some differences that have relevance when you write. (not only the number of gods but for example how gods are worshiped or how are the followers building temples)

Read about real religions: this is a good base for understanding how religion works and you are going to see a lot of how to write the followers.

Decide the characteristics of the God/s: After have a clear idea of what you want to do (example: religion similar to Romans’ one or a mix between Egyptians and Greeks gods) you have to clear up some points:

1. Is you god/s good or bad? : so how are they seen by the people, what are they famous for, how is their temper, are they revengeful or are they forgiving, if they are feared or loved or both. If you create more gods then you can decide to make them represent something.
2. Are your god/s in contact with mortals?: The relationship with mortality; If they don’t meet mortals you have to decide if they communicate with them and how.
3. Physical appearance: if they have a physical appearance describe it or describe characteristics that the god have when in physical form.
4. Worship: While the points before where about the point of view of the God/s, you have always to define how mortals venerate God/s.
5. Is all the population religious?: This is important because there you can determine the relationship between who believes and who does not or between different religions. Or say if is imposed.

Other points of interest :

1. What role have religion in the State: So if religions have a political power, how much power do they have and if is used for good or for bad.
2. What are the religion institutions: Is there a leader of the religion, what are the offices and how they are built, how much the institution influences the population.
3. Where: where does the faithful worship God/s (temples, groves, churches, or at home)
4. HOW: this is probably the most important aspect. Here you need to define how people practice their own religion, so if they only pray or do make sacrifices, if there are rules that influence the daily life, if there are festivities or particular ritual, if there are symbols that are worshiped.