At certain points during an adventure, the AI will pass its turn as its first action. I'm guessing it has to do with positioning on board and not cards in hand. When this happens if you do not move and the adventure does not have a victory condition based on time a party with at least one priest can exploit this. Simply cast your healing spells and end turn go through your deck a couple of times times this way and bring every party member to max health. i did search forum for similar, but ended up with 0 results.