At the end of some adventures, quest items are automatically awarded to unlock follow-up adventures. They act as keys to enter and are consumed at the start of an adventure. Thus, they encourage the player to successfully complete an entire chain without wiping out the party. They also serve as plot devices that link different parts of an adventure chain.
This chain is unusual, in that completion of A Feast of Thieves forces the player to choose between two items; each item allows access to a different follow-up (The Hand that Feeds or Army of the Night).