First appearance: Clockworks #1
Use: Opens the Black Door
Door: The Black DOor
The Omega Key was the first key to be crafted. When Benjamin Locke was hiding in the caves with the revolutionaries, they accidentally opened the Black Door and some of the Children of Leng came out and immediately turned to Whispering Iron. Once Benjamin realized that regular steel was insufficient to hold the door closed, he crafted a padlock and key from the whispering iron itself. Later, the lock was modified to be part of the door itself.
The key was only used to obtain Whispering Iron, and no infestation of the Children of Leng was recorded until the Tamers of the Tempest made their attempt. After the events of that attempt, Rendell Locke vowed to make sure the Omega Key stayed hidden for the rest of his life.
After Dodge came back and started hunting for the key, it remained hidden until it was found in Rendell’s cremated remains. Tyler Locke then attempted to hide it in his head using the Head Key, but Dodge (in Bode Locke’s body) eventually gained possession of it.
Guide to the known keys entry:
(damaged) …another dead & the…dore open againe…the things turned to irone…in our w…& I resolved to use them to crafte…hazzarded such a lock wood hold…long I worked in a fever’d…till finallie t’was cast &…oh how I feer’d! My har…in the gathr’d dark… straiked out &…held the dorr…beig’d God… Gonel…hold”
Source: Locke & Key Wikia