When directed to add a monster to the adventure cards... What do you do if NONE of the current adventure cards (including the new one that replaces a trophy just taken) has no indicated slot for a monster (partial or full)?
Do I not add a monster? Is it a get out of jail free card?
From the rules on page 11.
"If there are no monster tasks in play not already covered by a Monster marker, the active player chooses any 1 Adventure card and places the Monster marker under the bottom task of the card, adding an additional task to the Adventure card."
Plus, it is worth noting the official FAQ states
"When placing a monster under the bottom task of an Adventure card if there are no available monster tasks in play, players must distribute monsters as evenly as possible. That is, no Adventure card may have a second monster placed below it until all Adventure cards have at least one monster placed below them (and no Adventure card can get a third monster until all have at least two, etc.)."