As there is apparently no thread that handles the new secrecy mechanic, I am opening this one to discuss the concept itself, strategy and the cards using the secrecy concept already. Players can also share their experience with secrecy decks. I'd like to begin with some general thoughts:
1) The concept
I have to say that I wasn't a friend of the secrecy concept when it was announced by FFG. Why should I do with one hero less only to be able to play some cards with lesser costs? I thought this to be less fun, because of the lesser variety of heroes, and not very helpful to increase my chances of winning the game. Ok, perhaps secrecy might work in a multi player game, but as I am playing in solo mode only, I was less than excited.
However, I changed my mind once I was using secrecy in Juicy's tournaments playing Road to Rivendell. The scenario is not very difficcult, that is, but still I could see how the secrecy mechanics worked in my favour. One of tbe first things I realized is that the low starting threat helps you to build up your deck before the nasty enemies can attack you. In most of my games I didn't make much progress in the first three turns, because either I had a lot of enemies waiting in the staging area or I had to explore several locations, but once I had enough allies in play, my fellowship was almost unstoppable.
I don't want to get into a discussion about RtR strategy, but those who played this scenario know that one has to be careful to engage with an enemy because of the brutal shadow effects in this game. That's why secrecy is more than handy, as you can choose if you want to engage an enemy or not (except for Goblin Spearman). Enemies like Wild Bear or Mountain Warg will never engage you, if you don't want them to.
2) Threat management
Of course starting with a low threat is not enough, but you have to keep your threat low to use the secrecy mechanic. I feared that this might be difficult, as there are only few cards that can lower your threat (but more if you onw more than one core set). However, I played 9 games so far and only one or two times my threat was over 20 points. Threat management is thus doable, even more so as there will be coming more cards that are threat lowering.
3) Secrecy cards
There has been some discussion already about the usefulness of "Out of the WIld". For one lore resource a player can possibly get rid of a dangerous encounter card. That's pretty much awesome, but for me this is not the best secrecy card.
My favourite is "Timely Aid", as it can give you a costy ally for one leadership resource only. Especially early in the game this card is simply the best you can play, especially if you build your deck around this card, adding lot of 4 or 5 cost allies. Imagine Gildor Inglorion joining your fellowship in round 1 (his special ability btw works fine in combination with Timely Aid)! Or Beon. Or Brok Ironfist. Even allies from other spheres can be played via Timely Aid.
The third card I am using right now is "Dúnedain Wanderer". He is not that helpful in RtR, as I avoid fighting if possible (and have Mirkwood Runner for killing enemies), but in other scenarios it's nice to have a solid fighter early in the game. And in multiplayer games this guy should rock, having both the Sentinel and the Ranged keyword.
"Needful to Know" isn't in my deck so far, but I plan to use it next time. Obviously this card works well if you have either Denethor or Henamarth Riversong. Lowering your threat and paying nothing for it is great.
4) Heroes
Perhaps the most important question is the choice of your heroes. You can only pick two which makes each hero's advantages and disadvantages an even more important issue as it already is. There are several categories which are important for your hero choice:
a) Sphere
All of the four secrecy cards are from either the lore or the leadership sphere. "Resourceful", which will be in TWitW is a neutral card. One or better two of the heroes should belong to these spheres. As the spirit sphere has all the cards to lower your threat, spirit heroes are also a good choice.
b) Starting threat
The lower, the better. In my opinion the maximum starting threat of both heroes combined should be 18, otherwise a player is probably not able to use the secrecy keyword at all.
c) Special abilities
A hero should have abilities that make up for the lack of a third hero. Additional attacking, defending, questing, resources, cards etc is what you need in a secrecy deck.
Heroes who thus qualify for a secrecy deck are:
Lore: Beravor, Bifur, Bilbo, Denethor, Glorfindel
Leadership: Aragorn, Dáin, Glóin, Théodred
Spirit: Dwalin, Dunhere, Éowyn, Frodo
Dáin should obviously only be used combined with another Dwarf (preferably Bifur). I left out the Elladan and Elrohir, because they're only useful if used together which makes a starting thread of 20. Also their abilities can only be triggered if they're not questing. Prince Imrahil didn't make it on my list, because his ability triggers only when an ally leaves play. In a secrecy deck you need every single ally, so his ability is mostly a waste. Eleanor has a low starting threat, but her ability is not very helpful to compensate the lack of a third hero. All other heroes not listed are either from the tactics sphere or their staring threat is too high. Glorfindel and Aragorn are in the list, but they have to be combined with a hero that has a starting thread of 7.