The way deck-building works in the game is that after you finish a scenario, you have the opportunity to keep, trade, or banish the cards your characters acquired. The cards you chose not to keep are sent back to the Vault (possibly to be encountered again later).
Aside from the character's decks, you do not build up a "library" of shared cards to manage between games. Deciding which cards you keep after a scenario can sometimes be a difficult decision, because for every new card you want to keep, you'll need to swap it for a card that a character already has in their deck.
Edit: Also, welcome to the forums! Glad you're enjoying the game.
The way deck-building works in the game is that after you finish a scenario, you have the opportunity to keep, trade, or banish the cards your characters acquired. The cards you chose not to keep are sent back to the Vault (possibly to be encountered again later).
Aside from the character's decks, you do not build up a "library" of shared cards to manage between games. Deciding which cards you keep after a scenario can sometimes be a difficult decision, because for every new card you want to keep, you'll need to swap it for a card that a character already has in their deck.
Edit: Also, welcome to the forums! Glad you're enjoying the game.
Oh, ok .. that makes more sense than ...
THanks!