When I am ready with my adventure I have to set the decks right for each adventurer. Sometimes I see an exclamation mark (!) on the cards. What does this mean ?

That means your deck is "illegal" so you either have to get rid of something or take something.

 

For example if you have a character that can only have say 3 blessings and you have 4 in your deck then you need to get rid of a blessing. Conversely, if you need 3 blessings and only have 2 then you need to take another blessing. The game won't let you progress until all decks are legal and no exclamation points remain.

That means your deck is "illegal" so you either have to get rid of something or take something.

 

For example if you have a character that can only have say 3 blessings and you have 4 in your deck then you need to get rid of a blessing. Conversely, if you need 3 blessings and only have 2 then you need to take another blessing. The game won't let you progress until all decks are legal and no exclamation points remain.

Answering my own question.  

 

If the deck is illegal the numbers ofd the cards are in red. I think the ! means that those cards were added in the scenario which was jus played.

Yes, that's correct, at least that's what I figured that meant!