The bow is a highly intelligent weapon, with memories and plans. The wielder of the bow is a brainless zombie, who is still perfectly capable of wielding the weapon. Together, they're an NPC.
An unstrung and useless piece of cold wood, unless you happen to be dead.
Suddenly an east wind blew, and far above the clouds rolled and folded. Where there were once whisps of white there was now a long cloud formed in the shape of a recurved bow. Malakh bowed her head in humility. "That which you have asked is granted you, O Warrior."
...Vaakri reached and stretched, grasping at the sky. At first he seized nothing, but his heart was filled with the Empyrean Emir's winds and light, and finally he grasped the bow from the far sky and drew it to the earth.
- The legend of Vaakri
An ancient relic from a bird worshiping time.
"Tired of lugging about heavy quivers full of arrows?"
"...and thus it was said that Adaleer the Blest could reflect the true nature of any soul. Now some of his followers believed that his ranger gear, as much a part of him as his faith, was also so blest."
- Dauneth, Lore Chronicles
If you want to add a "supernatural" touch to your campaign, define the rules of magic and the universe. Make your players comfortable with those rules. Then your new supernatural creatures must then break those rules.