Adventure Reward: For the rest of the Adventure Path, after you rebuild your deck, you may banish a card from it to choose a card from the vault whose level is #-2 (minimum 0). Adventure Card Guild players choose the card from their deck box instead.
Is it intentional that the card must be level #-2 instead of maximum level #-2?
According to a Discord post by Keith Richmond, #-2 is indeed meant to be "maximum". Additionally, the chosen card gets added to your deck (which isn't actually stated anywhere in the currently-written reward - it just says to 'choose' a card, not what to do with it).
Sounds like an error in the text (intent is that you can choose 0, 1, or 2 at level 4) - we'll fix it in 7-3
A reminder that this occurs after rebuilding your deck, so you can use this to tweak the card types comprising your deck (like switching out a weapon for another spell, for example).