Duress is a nice card. If your opponent knows what they're doing, the hand they start with is one that they feel will give them a good start - otherwise, they would've taken a mulligan. Duress is especially nice if you're going first - drop a Swamp, throw out Duress, and get a sneak peek at what the next few turns are going to look like. Aw, were they counting on that Rampant Growth to grab their off-colour land? Was that Lightning Bolt going to zap your Deathbringer Thoctar before it ever had a chance at life? Was their Mindlock Orb going to shut down your later Diabolic Tutors and Liliana Vess? Forget about it. And if Duress is a nice card, Thoughtseize is a fantastic one - albeit about fifteen times more expensive, for obvious reasons.

Forget about Duress and Thoughtseize - what about Raven's Crime?

A dozen cards from the Eventide set feature the 'Retrace' option (recommended reading: Steve Sadin's 'Lessons from Retrace'). I really like the idea, even if I can't help feeling a little disappointment that these 12 don't allow for a slightly wider range of effects. But given the choice between playing a first-turn Duress, and a first-turn Raven's Crime, which would you pick? They're evenly matched for both cost and speed. There are three key differences. First, that Duress lets you look at your opponent's hand. Second, that although Duress lets you choose the card to discard, it only allows a narrow set of options - if your opponent is holding a dual-land and a Master Transmuter, then you're out of luck - while Raven's Crime always knocks off at least one card, even if it's the least-useful to your opponent. Thirdly, and most importantly: on turn ten, when you've hit a land-pocket and you're hoping that your opponent isn't holding the Cancel that will ruin your eventual top-decked tie-breaker, you can take comfort in the face that you can keep retracing Raven's Crime to ensure that the other's player's hand remains empty.

Sound like a bit of a stretch? Imagine a similar situation, except that your Knight of the Reliquary are just barely holding it down late in the game - wouldn't you love to retrace Spitting Image, copy whichever creature is making life hard for your Knights, and pump them up another +1/+1 at the same time? Retrace is tough to deal with for the other player - a Counterbore is normally devastating when countering the first instance of a key card, but if that card has retrace, you could almost argue that it helps you - remove the now-redundant copies from your library as the retraceable card falls safely into your discard pile. I mean, who plays graveyard removal?

It's a usefulness that's situational, to be sure, but not something to dismiss. Reusable cards are always something to pay attention to.

  

Basically, this is all about mitigating those disappointing draws later in the game. It's disappointing enough to draw something you can't use when you're ahead, or even when you're behind, or when you need an answer to progress - it's pretty discouraging. So picking cards that will be more conducive to later use can go a long way towards smoothing rough edges and securing a little much-needed card advantage.

  

Speaking of Knight of the Reliquary - why are they so good? Think about this - turn one, Terramorphic Expanse for a Plains. Turn two, Fieldmist Borderpost and the same Plains. Turn three, drop a forest, and the Knight, who is already a 3/3 thanks to the Expanse. Next turn, keep your knight as a blocker - and at the end of your opponent's turn, tap him to swap the Plains out for a Seaside Citadel. It comes into play tapped, but that doesn't matter - your turn begins, you untap, and suddenly your mana is fixed, and your knight is buffed. You've also achieved another interesting result - there is now one less land in your deck, that is to say, you're slightly more likely to draw something other than a land. The more land you pull out with the Knight and Expanses, the more likely you are to draw something else that will be (arguably) more useful - Behemoth Sledge, for instance. This has been refered to as 'the theory of Deck Thinning.'

   

Alternately, instead of increasing your chances of drawing the card you need, you can simply ensure that you're drawing more cards - the use of 'cantrip' cards will help you filter more quickly through the randomness of your deck and arrive sooner at the card that you need. In addition, careful selection of cantrips make the card's other effect as important as if not more important than the draw action itself. Snakeform gives you a surprise combat win even in what would otherwise be improbable circumstances - your Fatestitcher is suddenly able to block an opponent's Enlisted Wurm with ease. So for three mana, you kill a creature and draw a card - seems like a pretty good deal to me. Elvish Visionary is pretty wimpy, but comes with a free draw - plus he's an elf shaman, with all the tribal benefits that those attributes bestow. Manamorphose is, at the very least, a free card - it makes as much mana as it takes to cast - but there's the added benefit of mana fixing, especially in a Jund or Naya coloured deck. When you've got a very focused deck list ('4-of's of a small number of integral cards) you're essentially using this card as a 'placeholder' - whenever you draw it, you might as well be drawing whatever's next. It's filler that doesn't hurt you to include. Ponder is a similar situation, although it adds a little extra spice to the usual cantrip - you actually get to pick your draw out of the top three off your library, and re-order the remaining two! Combine that with a Harbinger-like effect (Merrow Harbinger being the obvious example) to turn it into a tutor instead of a harbinger, for only one additional blue mana. Think of it this way - is it worth including another arguably less-useful creature to pad out your 60-card minimum, or would you rather keep your list lean and mean?

   

Finally, there are some cards, creatures especially, that grow, or evolve, over the course of the game. Some of them, like Figure of Destiny or Jenara, Asura of War, get bigger the more mana you dump into them - the key being that this power/toughness increase (and ability addition in the case of the Kithkin) are permanent additions. Normally you'd have to cast additional spells to give creatures these permanent boosts - so you're getting the same effects, but spending less cards. Some of these 'growers', like Scarland Thrinax and Vein Drinker, thrive in a certain board state - the Thrinax wants to eat your other creatures, while the Vampire just wants to eat, starting with the smallest meal first, and working its way up until even something as big as Doomgape doesn't phase it. Combined with something that allows you to trigger that ability multiple times (even something as ridiculous as Act of Treason), your Vein Drinker very quickly achieves on its own what would normally take other creatures several turns and several spells.

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So when you're building your next deck, and you're a little worried about running out of steam later in your game, remember - you don't have to field a Blue card-drawing engine in order to secure card advantage. You can choose cards that continue to grow even after you're played them, and you can take steps to reduce your chances of drawing cards that you don't need, and you can choose exploitable cantrips. Obviously, you don't want to focus on this aspect to the detriment of the rest of your strategy - but if you feel like you have an idea that's almost working, consider what card advantage can do for you to help secure your win condition.