I find it weird that this card has only one review, so i decided to make sure that everyone know this is the second best card in the game, after steward of gondor. If you're running lore, you need to run this, 3x. It makes you go through deck way faster, and the selected discard means you can ditch the least useful (or useless) card at the moment and keep going. It's a card that makes foundations of stone a good expansion to purchase multiple copies of.

First off, something needful to know about this card; it is not scrying and threat reduction in one.

Let me explain. Scrying is primarily useful when knowledge of the encounter deck is uncertain (i.e.; you use it to know what's coming up in the turn ahead.) This means that, logically speaking, you should play Needful to Know when you have no clue what's on top of the encounter deck.

Threat reduction, however, is primarily useful when it's consistent. When you play a threat reduction event, you want to know that it is going to drop your threat enough either to avoid threating out or an unwanted enemy engagement. In addition, for the majority of decks, just like resources or card draw, the more you reduce your threat the better off you'll be. This means that, logically speaking, you should play Needful to Know when you know exactly what is on top of the encounter deck.

Playing Needful to Know as both a scrying card and a substitute for The Galadhrim's Greeting thus leads to a paradox; in order to obtain the greatest gains from playing it, you want to play it when you have no knowledge of the top card of the encounter deck and exact knowledge of the top card of the encounter deck. Needful to Know is two halves which, combined together, don't compliment each other but actually work against each other.

The key to using Needful to Know effectively is to decide which of the two functions you want to focus on more. If you want to use it for scrying, include other methods of threat control and content yourself with lowering your threat by 2-3 overall. If you want to use it for threat control, pack other scrying so you know when to play it for greatest effect. Don't try and make Needful to Know be both things at once; it's not that Needful to Know isn't strong enough to fill both needs, it's that no card can ever manage to solve the paradox Needful to Know raises, where in order to reach its maximum effectiveness it is needful to know both nothing and everything about what the top card of the encounter deck is at the same time.

Either that or play it with no knowledge of the top card of the encounter deck and pull off a thematic win by doing something Tolkien himself did; pray.

A perfect complement to this card (which doesn’t exist) would be one which places a random enemy or location on top of the encounter deck. Then the scry would be useful and you’d have guaranteed threat reduction. It’s only the treacheries (or uncommon X threat locations/enemies) which cause the threat reduction to miss. —
For me, it's card draw and threat reduction. This triggers the hobbit pipe, and works wonder in a support deck with some scrying. With this and shire-folk, you don't have to play the expensive smokerings. —

This card has good use in the questing phase to mitigate location threat. On some occasions I have been able to use them in a combo with Éomund where Riddermark's Finest quests for one, then is readied and can use the ability. Alternatively, one could use the action in the planning phase and be saved by Gamling only to repeat the same action.

One last bonus may be the "creature" trait which can be used in favor of decks thriving of creatures, or even encounter card manipulation at times. I do believe there is an encounter card or two which can be cancelled by discarding a creature - a special tech in that case.

"That is no orc horn..." Nope. It's tons of cards entering your hand every game.

This is the card draw Rohan has been thirsting for. Until Horn of the Mark was released there were limited options for ensuring those allies and tools would see your hand in time. Horn of the Mark is THE card which almost single-handedly rounds out the Rohan archetype as the final packs of the game are released. It seemed odd to me that Horn of Gondor previously had one of the best synergies for "ally leaving play" attachments in Rohan decks. HotM replaces this without question, especially with Théoden helping reduce ally costs already.

While Spirit/Rohan card draw may be a blessing in itself, Horn of the Mark can pair with hobbit decks to some extent so long as Merry joins the party. Who knows, perhaps Nor am I a Stranger may even make it's way to more decks. With the primary action ability of Rohan discarding or leaving play the payoff is huge, and even more so when Gamling is there to save them. Even the cards which temporarily put Rohirrim onto the battle field such as Lothíriel and Horns! Horns! Horns! will get more cards into your hands for no extra cost.

Horn of the Mark has quickly become a Rohan staple. If you love building Rohan it is a must.

This card is definitely awesome and an amazing addition to the Rohan decks, even though Lothiriel could be its best interaction. I am not sure about the part you mention regarding Muster of Rohan. Since you must exhaust the Horn to draw a card even if 4 allies are leaving play you will still draw only 1 card. —
Woops! That moment you realized you overlooked a huge aspect of the card! Thanks for pointing that out. —

I hardly think this guy needs any introduction. I started officially playing the game within the past year - well after Gamling's release. From my understanding he was a Rohan game-changer. Its hard to imagine a Rohan deck without him. That's how essential he is. I love to build Rohan decks and every time I build with Théoden Gamling has been there saving the day. In my opinion, he has reached "auto-include" status is nearly every Rohan build.

When you do not have any intention of discarding Rohan allies he still boasts a decent 2 and 2 HP. Considering is ability this is not bad for an ally who is saving other discarded allies. Théoden knocks off one resource to his cost allowing Gamling to enter the battle rather quickly. He can be a backup quester when you need it, or if you intend on ensuring Éomund will ready him later. Otherwise, you're likely going to find yourself using him purely for his ability, or taking your chances blocking a weaker enemy.

He adds special value with the Messenger of the King contract as well allowing you to pump out Rohan allies with Théoden, discard them through the card effect (or Ride to Ruin/Helm! Helm!), then save and repeat next round. You can't save them all, but you can sure as heck slap Unexpected Courage on him (for MoTK) and save two. He will also save you up to 2 card slots in a deck this way.