The Science of Runic Casting
The discovery of rune magic allowed everyday objects to be enchanted to perform basic magical tasks that would otherwise require a mage to actively cast. This greatly improved the everyday comfort of the general populace as it made magic available to all regardless of their personal aptitude. Runes do require periodic maintenance to ensure they remain properly attuned to the correct magical fields. The more complex the runes the more frequently they should be inspected, as malfunctioning runes could have unintended side effects.
The effects of runes are varied and highly specific to the particular runes utilized. It is hypothesized that there are runes for enacting any possible magical spells, although many of the required rune combinations have yet to be discovered. As with all magic, runes are also subject to the Third Law of Magic, causing permanent changes in creatures experiencing long-term exposure to a particular magical effect. Most applications of runes would cause minimal exposure in the long term with no adverse effects, but care must be taken when using large industrial concentrations of magic, even in rune form.
Runes draw power from the surrounding magical fields, attuning the runed items to the selected magical types and directing the items to perform a particular task. This allows the items to dictate a particular set of magical commands rather than requiring a mage to do so. The more complex the task the more complex the runes and the more frequently a trained mage should inspect the runes for any sign of damage or magical disalignment.