My antagonist had a pair of intelligent blades; artefacts forged by the God of Death and Destruction, bound with the intellects of demons.
Kage Daishou was the katana, Kage Shotou the wakizashi. Blades black as night, the God of Death planned to have them corrupt him into a force of mad destruction as the demonic minds imposed their will on his.
Fortunately, he had a lucid moment, realised what they were, and tossed them into a volcano to get rid of them. Unfortunately, the volcano erupted. He stopped, faced the flow, and let it consume him.
Since then, no intelligent items have appeared in the storyline.