The collecting spider, created by a tinker who was known to be stingy even for a goblin, is a 2-foot high, 4-legged mechanical device that has a powerful magnet attached to its abdomen. When it passes over anything metal that weighs less than one pound, the magnet attracts it. The tinker discovered she could save a lot of money on arrows and crossbow bolts, but she still waits for the day she picks up someone’s long-lost magic ring.
The spider’s clockwork is powered by the magnet as well, cleverly designed to run from the magnetic field that sits below it. It walks forward for 20 feet, steps one step to the right or the left (determined by a switch) and then walks back. It continues doing this until switched off or until it runs out of phlogiston. If it meets an obstacle it cannot cross, it goes around it. The spider can carry up to 10 pounds of accumulated metal (any more than this and it cannot move).