I'd like to see this clear:

When a character enters a challenge as attacker or defender, is it irrelevant the method used to do so?. I mean, is it considered to be "declared" even if he was played from hand or entered the challenge via an ability?.

A friend of mine showed me a part of the rulebook that seem to say so. According to this:

I'm the defending player. An opponent declared a challenge agaisnt me and knelt a character of STR 4. Let's say Walder Frey is in play and standing.

Now, I use The Wall to put a Night Watch from my hand as defender. Is that considered "declaring" a defender and so Walder Frey will now kneel and be in the winning side?.

Aertes said:

A character is "declared" as an attacker or defender if it enters the challenge in the usual way - by being assigned the status by the player during the framework action events specifically allowing a player to do so.

If a character enters a challenge in any other way (through card effect), it becomes a "participating" character, but it has not been "declared." When you get to challenge resolution, it only matters that a character is participating - no matter how it got there - but for the purposes of activating passive effects or triggering Response effects, "declared" is very specific.

Aertes said:

Thats what i thought, but then he shows me page 14 from rulebook, Step 2 of Resolving Challenges.

There it says "Kneel characters (or enable them to participate by some card effect)". My friend says that those brackets means that any way of enabling a character to participate in a challenge is the same as "declaring", and I don't know how to discuss against that.

This passage refers to characters like the KL Knight of Flowers, that don't kneel to attack or defend. When a character enters a challenge through a card effect, like the Greatjon or LoW Catelyn or when you use The Wall, they do so at an entirely different point of time.

Ratatoskr said:

It's more about cards like Ser Balon Swann, while he has no intrigue icon.

Aertes said:

"kneel any number of his or her characters
that have the corresponding challenge icon
(or are enabled to participate by some card effect)
to defend against your challenge."

Aertes said:

Consider the fact that you can use abilities that would put characters into the challenge as a defender "Before and between (but not during) each step" (see pg. 13), meaning that you can get characters into the challenge as defenders outside of the "declare defenders" step. That's the whole point. Card effects used outside that step do not qualify as "declaring" the defenders.

You friend is giving too much weight to the "short version" of the description of declaring challenges. It does not take into account the more advanced description of the timing (both overall and for challenges) in the FAQ.

Once again, thanks a lot all.