So I'm trying to put together a deck that uses Tunnels of the Red Keep and a bunch of characters in shadows.

So my questions are as follows;

1) If I have a unique character out who has the shadow crest, can i attach a copy of him for free or do i have put the character into shadows but i can then bring it out for free as an attachment at the start of the next phase?

2) If I don't have to put the unique character into shadow's to attach him, can i still put the unique character into shadows so that I can get the benefit from tunnels?

3) If 2 is true and I have a unique kingsguard out with his dupe in shadows, can I use Ser Barristan Selmy's ability to kneel 1 influence or pay 1 gold(provided it is the challenge's phase) to attach said characters dupe to save him from a kill effect by immedietly discarding said dupe?

1. It's your choice. You are allowed to dupe from hand during marshaling for free just like any other unique character

1 & 2. Keep in mind that while you can dupe with the Shadow card directly from your hand for free, if you decide to put the card into Shadows and then bring it out to dupe, you have to pay the full cost (2 gold to put into Shadows from your hand, plus whatever is after the "s" to bring it out of Shadows).

3. doulos2k's warning about the timing is true. You can use the trick you mention to dupe a unique Kingsguard character in the middle of the Challenge phase and then save them, but you'll have to do it before the kill effect you want to save the character from initiates.

ok thanks for the quick responces, I guess I'm still not too clear on which effects can be used when.

My next question then is this,

Ser Mandon Moore's ability is Challenges: Bring Ser Mandon Moore out of Shadows and into play by paying the rest of his gold cost.

He then has Responce: After you win a challenge in which Ser Mandon Moore participated as a defender, choose and kill a participating character.

Can I use his ability after someone declares an attack on me and has declared his attackers to sneak Ser Mandon Moore out so that I can use him as a defender?

If I can do that can I instead use Ser Barristan Selmy's ability instead to save on gold?

Short answer: yes, you can use Selmy's ability to bring Mandon out of shadows during the challenges phase to save on gold (paying 1 for Selmy's ability rather than paying 2 for Mandon's).

Mandon's response ability is not predicated on using his Challenges ability to bring him out of shadows. Once he's out of shadows, he can trigger his response whenever the restrictions have been met. (This is unlike effects like Meera Reed or Guardian Wolf whose primary effects require you to pay the rest of their actual gold cost.)

"Can I use his ability after someone declares an attack on me and has declared his attackers to sneak Ser Mandon Moore out so that I can use him as a defender?"

This works. Both players can trigger any number of Challenges (or Any Phase) player actions between the attacker declaring attackers and declaring who he stealths (if applicable). Declaring stealth comes immediately before declaring defenders. You cannot bring Ser Mandon into play after your opponent declared stealth.

I too have a shadows question.

If I bring Blackwater Raiders out of the shadows (response: after they come out of shadows, take a location from your opponent's discard pile and put it into play under your control) and take my opponent's discarded The Blackcells, can I then use the response of my Raiders coming out of shadows to trigger the newly acquired Blackcells?

Sorry if this question sounds confusing. I would appreciate an explanation as well. Thanks a lot!

Well, maybe. Responses to cards coming out of shadows starts with the player to your left. If your opponent chooses not to trigger their Black Cells before you steal it, then yes you could trigger it. But, the more likely scenario is they will have already triggered it and you'd be taking control of it already knelt.

Well, since you're taking Black Cells out of the discard pile, the opponent would definitely not have triggered this particular copy's response. And yes, you can use the response on Black Cells, because you're still in the response window for "after a card comes out of shadows".

Ok new question,

If I have Meera Reed http://www.cardgamedb.com/index.php/GoTCards.html/_/a-tale-of-champions/tourney-for-the-hand/meera-reed-tfth and Arya Stark http://www.cardgamedb.com/index.php/GoTCards.html/_/kings-landing/city-of-secrets/Arya-Stark-CoS

in play and someone Valar's

Do both of them go back into shadows?

No. Arya would, of course, but both cards become moribund simultaneously. Meera is moribund:dead while Arya is moribund:Shadows. Without a save effect, Meera could not trigger her response and go to Shadows. And once a card is moribund, you can't change its moribund destination without a replacement effect.

Arya has her own replacement effect. Meera's response is not a replacement effect (it lacks the word "instead").

Another shadows question:

Plot card: Called To Court

When revealed, each player may put an in-House character of printed cost 3 or lower into play from his or her hand. Each player must choose 1 character he or she controls and return it to its owner's hand, if able.

I assume that I can put a shadow card with cost S1 directly into play using this plot card - the shadow requirement being just a marshelling mechanism ... is this correct?

Correct. The printed cost is 3, so you can put it directly into play as such (other put-into-play effects also bypass the requirement for shadows, like Ambush from the Plains).