The presence of magic in your game world forces you to deviate from a truly historical setting. When you create anything for your world, the idea that magic could possibly alter it should be in the back of your mind. Would the king simply surround his castle with a wall when levitate and fly spells are common? How do the guards of the treasury make sure that someone doesn’t just teleport in or slip through the walls while ethereal?
Unless you are going to run a divergent game of some sort, magic is prevalent enough in the world that it will always be taken into account by smart individuals. A merchant wouldn’t be flabbergasted by the idea that someone might try to steal from her while invisible. A swindler would be aware that someone might be able to detect his thoughts or his lies.
Magic shouldn’t be something that common people are unaware of. Spellcasters may be fairly rare in the big picture, but they’re com-mon enough that people know that when Uncle Rufus falls off the back of the wagon, they could take him to the temple to have the priests heal the wound (although the average peasant probably couldn’t afford the price). Only the most isolated farmer might not see magic or the results of magic regularly.
Here are a few points to consider when fitting magic into your world.
• A tavern frequented by adventurers might have a “No detections” sign above the bar to allow the patrons to relax in an atmosphere where they don’t need to worry about someone discerning their alignments, reading their thoughts, figuring which of their items are magical, and so on.
• Merchants might jointly employ a small squad of wizards who wander about the marketplace invisibly while watching for thieves, casting detect thoughts on suspicious characters, and using see invisibility to look for magic-using robbers.
• The town guard might employ a spellcaster or two (or more) to supplement its defensive strength, deal with un-ruly spellcasters, and help facilitate interrogations.
• A court might use detect thoughts or discern lies to help make accurate judgments in important cases.
• A town might use simple spells to make life easier, such as continual flame to make a sort of streetlight. Very sophisticated or wealthy cities might use magic portals to dispose of sew-age and carpets of flying to deliver urgent messages.