An eldritch artifact from my current Silent Legions game.
That would make a pretty good macguffin needed to slay some beast of legend, or to play keep-away-from-the-villain with. Otherwise it seems like giving your party a timebomb. I guess that’s appropriate for the genre.
Do some users of the blade strike to injure, instead of kill? I could see cursing people with horrific visions and nightmares (if they were a lingering effect) in order to spread madness (or perhaps a cruel tool to punish wrongdoers in the hands of a misguided NPC vigilante) .
It would also be totally rad in a SWN game using the sanity rules. Everybody loves space katanas.
I suppose one could try to strike to wound and spread madness. But remeber, the blade doesn't like to be sheathed unless it has tasted death!
And the time bomb element is totally intentional! It will eventually bring ruin to its user.