Key
From SpiralKnights
A Key is a type of arsenal item that can be used to unlock locked containers or areas. The key section doesn't show up in the arsenal if the player doesn't own any keys.
Silver Key
A special key that can open any lockbox. Silver Keys can be bought from the Supply Depot or Kozma for 750 energy, and are destroyed once used.
Silver keys are tradeable and can be sold in the Auction House.
Shadow Key
A special key that can unlock the elevators into the Shadow Lair. It is obtained from Iron Lockboxes or the Supply Depot or Kozma for 1800 CE each. Only one is needed per party to unlock the Shadow Lair elevator, but is destroyed upon use.
Shadow keys are tradeable and can be sold in the Auction House.
Notes
To date, there are two types of keys that a player can have in the "Keys" section of the Arsenal.
The Gold Key object found in the Clockworks does not go into the player's arsenal. It is an object encountered in the field that simply serves as a means to progress through areas, similar to status and switches.
The 
Book of Dark Rituals and 
Fiendish ID Card are very similar to a Shadow Key. Each can only be used once per activity. To repeat the activity, another must be acquired. A single one can allow access for up to 4 players in the party. These items are stored in the material section of the player's arsenal.
