I thought I’d expand on and spin off some earlier discussions of magical devices. This turned into five sections that were all too short for individual posts, so here are the first three:
Magic items are a big topic in the fantasy and urban fantasy genres. As readers, we often want to see them appear in a story. As writers and worldbuilders, the urge to play with the Golden Fleece, Excalibur, the Philosopher’s Stone, flying broomsticks, magic staves, and cloaks and rings of invisibility can be difficult to ignore or resist.
But, magic items raise some important questions about the fictional world. Should such items exist? Can they exist, based on how the magic system works? How are they made? How strong should they be? How common are they? How long can they be used? Are they unique, mass produced, or a mix of both?
The answer to each question depends heavily on the intended use of the items, their effects on society, the feel of the setting, the feel of magic, and the world creator’s own sense of wonder. The last is, perhaps, the most subjective and variable. For instance, Tolkien’s magic items are rare and often powerful but they can evoke the same sense of wonder as Rowling’s magic items are everywhere world, just in different ways.
Assuming that magic items exist in the world, continue. If not, then the rest is irrelevant.
The power of magic items is of immense importance when we consider adding them to a setting. Generally speaking, the more powerful the magic items, the greater effect they can or will have on the world. They will probably also be less common or harder to make. Weaker items typically have less effect on the world, unless they are available and used in quantity. Careful thought into the strength of such objects is important, especially if anyone can acquire and activate them, as opposed to only being useful to a limited range of people (say, virgin Aztec males over the age of 40).
Sometimes the natural limits of magic restrict the strength of magic devices. Or the processes necessary to create magic items restrict their power level. In other cases, cultural laws can be used in-world to artificially limit the strength of magic items—ex. Steven Brust and Morganti weapons, J.K. Rowling and time turners.
A good example of varied strength comes from a comparison of Tolkien and Robert Asprin. Tolkien’s rings are world changing devices (literally), held by some of the most powerful beings in Middle-Earth (Elrond, Galadriel, Gandalf, the Ringwraiths, and Sauron). On the other end of the spectrum, Asprin’s d-hoppers are commonly available devices and a cornerstone of the multiversal economy.
Closely associated with the power level of magic devices is their availability. Are they rare and treasured (regardless of strength) or a dime a dozen? It is also entirely possible for a world to have both, some rare and powerful artifacts alongside hundreds of cheap and weak common items.
Availability can influence and affect both how the items change or shape society and the wonder or utility of magic items in the setting. In Fritz Leiber’s Lankhmar and Naomi Novik’s Polnya, items are rare and expensive, hoarded and doled out sparingly. In Rowling’s London, they’re household items. In Rick Riordan’s Camp Half-Blood, nearly everyone has at least one or two unique magic devices of at least moderate strength, whether this is Percy’s Riptide (sword-pen), Chiron’s concealing wheelchair, or Leo Valdez’s magic tool belt and Festus the Bronze Dragon.
If magic items are common, they can be used to create an entire economy in the world and affect daily life. These can include cleaning potions, magical light sources, and flying broomsticks. On the other end, if magic devices are rare, they become the stuff of legends and the goal of quests.