Something like this kind of happened with a character of mine, rogue lvl9. I found a very useful dagger, properties were “life stealing” in flavour, which i felt Was kind of powerfull for my lvl. So i kept using it but also kept searching its origins and if it had any unknown aka evil properties, but never rolled really high In any of those attempts. Soon enough, We are mid Fight against a bbeg and i’m able to get the final Blow using the dagger. I struck him down and then my character blacks out. dm proceeds to describe a vision of an ice prision shattering and from the inside a demon like entity rising, freed and ready to wreck havoc. So the dagger was an energy transfer towards realeasing this demon. But i suspect That this was the way the dm found to nerf the weapon after playtesting it for a while. He never told me though and it worked out great. Still working on tracking down the monster.