I've just received my copy of the game and I can see stack definitions in the back of each Quest cards. Is it a difference? Should I stack the exploration cards then?
Ok it's clarified now by Garrett (Budgernaut) on BGG.
That's not what it means by order. If you look at the enemy deck. There are two to three pictures of the enemy card back. Next to each picture is a list of enemies. The list of enemies next to one stack gets shuffled together, and the enemies next to the second image get shuffled together. Then you place the first stack on top of the second without shuffling. We agree on this, right?
Now look at locations. For each location, there is usually one image of a card back with the location name next to that image. If there are multiple locations next to an image, you shuffle those together, but again, each image represents a separate stack.
Now look at the exploration deck. There is only one image and a list of three tupes of exploration cards (e.g. base, dungeon darkness). Because this list is next to one image, all three are shuffled together. If the intent was to have separate stacks of exploration cards, the quest would show multiple exploration card backs.
An astute observer will notice that each quest has only a single exploration card back image, meaning that you shuffle all three exploration sets in each of the quests. Why, then, do they have the rule about stacks? Future proofing. The designers created the game with expansions in mind. It looks as though they thought stacked exploration decks would add too much complexity to the base game, but hoped to add that later. How would such an exploration deck work? Here are two of the many possibilities.
1) In preparing the exploration deck, place a unique exploration card between the two stacks. When you are at a certain location, it may say that you can't travel unless that exploration catd has been resolved. This would allow you to say, start in a village setting with Village exploration cards, but not be able to see the dungeon cards until you've explored the village and found the secret passage to the dungeon.
2) You could have a quest say, after you travel from location X, reveal exploration cards until you reveal a dungeon card. Resolve that card. This would be another way to have the feel of the game chsnge as you travel by making the exploration cards more closely match the locations.
You can see how both of these would add some complexity, which is why I believe they chose to leave a single stack of ecploration cards for the exploration deck in the base game. "