The Bronze Shield was a tool and piece of armor created by the Greek goddess Athena to aid Perseus in his battle against MedusaThe shield was known for its reflective properties, which was the feature that ended Medusa's reign of terror, at least on the mortal plane.
The shield was created at the same time as the Adamantine Sword and Winged Sandals, other divine objects created by the Gods Zeus and Hermes respectively as gifts to Perseus. Eventually, the shields reflective nature mirrored Medusa's gaze upon herself, freezing her as a statue.
The full capabilities of the shield are largely unknown. Being a divine shield, it can be assumed to be far more durable than regular shields. Additionally, the shield is very reflective.