From Pathfinder Treasure Vault (Remastered), which isn't enabled.

Swarming

ITEM 9

Price 700 gp

Usage etched onto thrown weapon

Bulk —

Able to copy itself many times over when thrown until the air is filled with deadly blades, a swarming weapon turns a single weapon into a shower of devastation.

Activate (concentrate)

Frequency once per hour

Effect You fling your weapon and it multiplies as it flies through the air, filling a 30-foot cone. All creatures within the area take damage equal to double the weapon's number of damage dice, with a DC 27 basic Reflex save.

Pathfinder Treasure Vault (Remastered)ORC