Artifact

An artifact is any unique magic item of which only one exists in a universe. Most magic items capable of being forged by mortals are relatively common knowledge, and thus many copies of them are created by many mages around the world. Artifacts, however, are not easily forgeable or reproducible, making them one-of-a-kind objects. Some possible origins of artifacts are: Artifacts are often items of immense power and are highly sought after in their universe. In many cases, an artifact can have a huge impact on the world when it is wielded by a mortal. For these reasons, artifacts often feature prominently in stories.
 * Forged personally by a god or demigod who only created one; requiring divine power to create, mortals cannot replicate it.
 * A relic of an ancient civilization whose methods have been lost to time; this single item is all that remains.
 * Crafted by a high-level mage using unique metamagic; the uncommon forging procedure isn't known to the rest of the world, so the item cannot be mass-produced.