The Crusher is a magic greatclub in Pathfinder: Kingmaker.
The description is misleading, this is a regular Oversized weapon with standard -2 Attack penalty.
Source[]
Drops from Branded Troll (Barbarian 5) who is attacking Bartholomew Delgado in the Wizard's Laboratory of Lone House.
This attack happen after appearance of New Troll Sightings event.