The way I originally imagined magic items was that mages interested in crafting these items would seek out/summon/capture spirits that were barely sentient or possessed a very pliable and low will. It doesn't do well for a fighter to have a strong willed nasty spirit refuse to swing during combat. For the most part, magic swords are magic swords, powered by a low level spirit, like an elemental that is practically mindless. There are some rare items though that might possess more sentience, and we might be planning to have some unique items that could have the ability to communicate.