Some episodes only use a subset of Keys. In this case, the episode setup instructs you to form the key repository using only specific Keys. 

Use only these Keys during the episode, unless it is specifically stated that the Key is taken from the supply. Return spent Keys to the supply, not the key repository. 

Clarifications:

• When the key repository is empty, do not rebuild it. You can no longer gain or place Keys on cards, unless it is specifically stated that the Key is taken from the supply.