It's prolly a weapon that a troll or wight genned with (esp if it's an OHE), since the new DISARM mechanics would prevent critters from picking up weapons.... and the only thing I can think of that would disarm there is skeletal soldiers if one wandered in there from the forest (which isn't common at all).
Starchitin, the OG
A severed gnomish hand crawls in on its fingertips and makes a rude gesture before quickly decaying and rotting into dust. A gust of wind quickly scatters the dust.