Sculpted by: Arlen Pelletier
Release: 2019
Edition: Legacy
Used material(s): Cast in bright chrome-plated white metal
One of: Unlimited

Signed: No

Reissued in Ghost Door box since 2020

First appearance: Keys to the Kingdom #3
Reveal hidden things
Harlequin Wardrobe

More information:
(possible spoilers)

The Harlequin Key is discovered by Bode in a hollow book titled “Keys to the Kingdom”, along with The Hercules Key and the Angel Key. Unlocks a door with a harlequin on the front.

Unlocks the Harlequin Wardrobe, revealing hidden things not seen when unlocked with an ordinary key.

Source: Locke & Key Wikia