Sculpted by: Israel Skelton
Release: 2011
Edition: Legacy
Used material(s): Cast in antique bronze plated tin
One of: Unlimited

Signed: Jay Fotos

First appearance: Keys to the Kingdom #3
Increases a key users physical strength and endurance
Hercules Necklace

More information:
(possible spoilers)

The Hercules Key was first seen used by Bode Locke in February, fighting for the Chain Key. It was later used by Tyler Locke the same month, and by Dodge on Scot Kavanaugh inside the caves.

The Hercules key makes the wearer three times as strong as they usually are.

Guide to the known keys entry:
Hercules Breastplate
(translated from German thanks to hideousenergy)

“Half of the 8th army and a seemingly endless bunch of SS-Men were waiting there for me! I hurled Eric against the wall and heard his ribs break, as if someone had jumped on a bundle of twigs. I have to admit it sounded like music to my ears! With the other hand I hit the soldiers and they flew through the air like matchsticks. The Hercules-Key released all the power in me that I had not possessed as a goddamn cripple. But the Sturmbannführer (a military title in the 3rd Reich army – Andi Preller) knew how to wear me down/ finish me off!”

Source: Locke & Key Wikia