Just a check as the rule book is not completely clear for me :

Let's say the principal quest just have an effect like "reveal an additionnal card during reinforcement", and let's assume that gather information is in the staging area.

At the beginning of the quest phase, you choose to make gather information the "active quest". How many cards will you reveal from encounter deck in reinforcement ?

The number of players, or the number of players + 1 ?

In fact, the question is more : is the text of the principal quest "active" even if the principal quest is not the active one ?

To the best of my understanding, making a side quest the "active quest" does not put any other quest out of play. Hence, all effects still trigger. The same holds in the opposite direction: even if an (encounter) side quest is not the active quest, its effects are still active as long as it is in play.

Yeah, tricil has it right. Side quests are meant to make your life hell. So Orcs will have +1 to all stats whenever Orc Ambush is in play, regardless of whether or not it is the current quest. And the main quest text, likewise, will remain active even if you choose a side quest to be the current quest. Some side quests say "when (this card) is the current quest, it gains:" ... so that text would only be active while that side quest is the current quest. But other text would not.

Ok clear and thank you

so far so good. I was going to post a similar topic but I'll just tack on to this one. So.... what about keywords? Those too? For example, if I am on a quest that has Siege and I play Gather Information, making that the active quest; am I questing with Defense?

Things get really weird! For example, lets say I'm playing Into Ithilien, the first stage; Ambush in Ithilien, has the Battle Keyword. There is a Southron Company in the staging area. My opening draw I get Gather Information and play it. Quest phase, I choose to make Gather Information the active quest. As I understand it (and somebody please correct me if I am wrong!) this is how the play proceeds:

1. I am questing using Attack power because Ambush in Ithilien has Battle, even though Gather Information does not have battle.
2. I draw Watcher in the Wood as my staging card. Its effects take place, but Watcher in the Wood does not gain surge because Gather Information does not have battle, even though we are still questing with attack power.
3. Questing resolves, Southron Company counts as 1 threat because the current quest does not have battle. I make some quest progress, but lets say not enough to clear Gather Information, so it is still in the staging area.
4. I engage Southron Company. Since side quests are only the active quest until the end of the questing phase, and it is now the combat phase, Southron Company has 5 attack value.

all these circumstances will all be repeated next turn of course, until Gather Information is cleared. Am I right about this?

awp832: If you look at the definitions of Battle, Siege and Defense, you will find an obvious answer. Namely, the keyword only counts for "characters committed to that quest" (the one with the keyword). Since the active quest is selected at the *beginning* of the quest phase, you only commit characters to the chosen side quest (you got points 1 and 2 incorrect) and the keyword of any non-selected quest does not matter for the remainder of the quest phase (you got point 3 correct). Outside of the quest phase, only the main quest matters (you got point 4 correct).

I made the same mistake, but a quick look at the definitions of Siege and Battle revealed what tricil mentioned: they only apply to the quest card on which they are written.

ok cool, that makes play a bit easier. ty.