Description: a hilt, sized for a human hand, on one end and a blue ball of light about a foot away on the other (the ball can be extended out another two feet, or brought in to a minimum of three inches). Connecting the two is a green line. Blade is designed pretty explicitly to not function if dropped, thrown, or ingeniously placed so as to eventually cause havoc, up to and including having it burrow down to the Earth’s core, while in the process causing a supervolcanic eruption that ends up destroying civilization in North America. Yes, somebody tried that.
Blade is not supposed to be a weapon: it cannot actually harm living flesh, which bizarrely enough includes integral parts of a sapient AI’s mechanical body. But it cuts everything else. Literally: nobody who knows about Blade knows this, but the item is designed to be able to effortlessly cut and slice neutronium. It’s the ultra-tech equivalent of a whittling knife. Note that Blade cannot thrust and cannot parry; inorganic materials are instantly sheared away and living flesh simply passes through the green line without resistance.
What it’s doing on modern-day Earth is anybody’s guess; scientists trying to figure out how Blade works are in the same position as Pythagoras would be if you asked him to reprogram your smartphone. If there are superheroes in the campaign world, one or more of them would be eager to have this item as the ultimate battlesuit can opener. If superheroes are not in the campaign world, people will be tempted to use Blade to become one anyway.