his Limited format is defined, in many ways, by mana Myr, such as Iron Myr. In addition to providing acceleration and a warm body (which can sometimes wield Equipment to become a particularly fearsome threat), they also count towards metalcraft. This can be huge—allowing you to turn your Chrome Steeds into 4/4s and your Vedalken Certarches from vanilla 1/1s into free Icy Manipulators.
Cards like Embersmith, Arc Trail, and Contagion Clasp are amazing in Scars of Mirrodin Limited in large part because of how many mana Myr tend to make their way into people's decks.
Even slower control decks that, in other formats, wouldn't normally have too many little creatures in them tend to have a good number of mana Myr because of all the benefits that they offer.
Mana Myr matter a lot in Scars of Mirrodin Limited. So while you might not end up with any mana Myr in your draft deck—either because you didn't value them highly enough and/or because you just didn't want them for your deck—you need to be aware of the popularity of mana Myr.
This means that you need to build your decks with an understanding that your opponent could easily get to four mana on his or her third turn.
While you might be able to, at least occasionally, spot a mana Myr-less deck in Booster Draft, in Sealed, it's a rare, rare deck that doesn't have at least a couple of mana Myr in it.
Heck, the color(s) of the mana Myr in your Sealed pool can even influence what colors you ultimately end up playing in your sealed deck!
All right, enough gushing about the importance of Myr. Let's take a look, in concrete terms, at how Myr consciously (and unconsciously) affect our play and deck-building decisions in Scars of MIrrodin Limited.
What Deck(s) Don't Need Myr?
Decks that don't care about accelerating, decks that don't care about metalcraft, and decks that don't have many good pieces of Equipment are generally indifferent as to how many mana Myr they have. The rest of the decks in the format really want them.
Decks that are based around good cards and big threats like Alpha Tyrranax (roar) and Molder Beast, rather than a particular theme, tend to need the acceleration that Myr offer (and it can be very nice to have a chump blocker later in the game if you are trying to wallop your opponent with a couple of really big creatures).
Aggressive red-white or white-blue Equipment decks can put mana Myr to good use by using them for a bit of acceleration early, and then turning them into serious threats a bit later by tossing a piece of Equipment on them.
Infect decks can commonly be found without a single Myr in them because they don't (or at least shouldn't) have any metalcraft cards, and a lot of their best cards cost three mana.
However, infect decks tend to be vulnerable to pretty much all of the same cards that mana Myr are vulnerable to so you won't have to adjust your play / deck composition on account of that (you will, however, have to make sure that your opponent doesn't blow you out with quick infect starts, but that's a different story for a different day).
Metalcraft Count (and When to Draft Myr)
Of all the decks that want mana Myr, no deck is better equipped to take advantage of the little mana-producing artifacts than metalcraft decks.
The general rule of thumb for metalcraft-heavy decks is that you want between fifteen and seventeen artifacts. If you are running a lighter metalcraft subtheme, you might be able to get away with closer to thirteen to fourteen artifacts, but even then, that will be pushing it a bit.
A couple of mana Myr in your deck will help you go a long way towards both enabling metalcraft at any point in the game, and towards enabling metalcraft early.
It is not at all unreasonable to see a player start the game off with a Panic Spellbomb, a Gold Myr, and then a particularly menacing turn three 4/4 Chrome Steed.
Because mana Myr are so good in metalcraft decks, and similarly (though not quite) as important in other decks, I am pretty happy to take a mana Myr as one of my first few picks in a draft. I know that I will be getting a card that I will almost certainly be able to put to good use regardless of what type of a deck I end up with.
Later on in the draft, I will take mana Myr according to my deck's needs. While there are few situations in which I would take a mana Myr over a premium removal spell or a bomb in my colors, I have no problem taking mana Myr over pretty much anything else in the set, if my deck has a great demand for it.
But if I already have enough mana Myr for my deck, or I am indifferent as to whether or not I pick up any more, then I will have no problem passing them if I see anything else decent that I might want to play.
How Many Lands (and What to Do with a Mana Myr?)
Once I've already picked up my second mana Myr, then I might still be on the lookout for a third, or perhaps even a fourth if I'm metalcraft, but my desire for them will drop significantly.
Perhaps the most common mana configuration that you will see in Scars of Mirrodin Limited, and the one that I generally tend to gravitate to, is sixteen lands, two to four mana Myr.
Even if I do have access to a bunch of mana Myr, and a lot of cards with metalcraft, I don't really like playing fifteen lands.
Why? Because while it is definitely important to fill your metalcraft deck with artifacts, I like being able to play my four-drops on turn three (which requires me to hit my first three land drops and play a mana Myr) and I want to minimize the mulligans that I have to take because I only drew one land in my opening hand.
However, there are players that are happy to drop to fifteen lands if they have three or more Myr and a couple of Spellbombs.
This means that you can reasonably expect that your opponent is playing between eighteen and twenty mana sources. Given that your opponent could easily be running a deck where every other card (or just a smidgeon under that) is a mana source—how likely do you think it is that you will be able to mana-screw him or her if you kill a second-turn mana Myr?
Not very likely.
Is it worth it to Fume Spitter or Contagion Clasp a mana Myr on turn two? The answer to this is generally yes.
Is it worth it to Galvanic Blast a mana Myr on turn two? Maybe, but unless I have a really fast or really slow start, or I know that I am going to be putting my opponent off of his or her splash color by killing the Myr, I will generally hold onto my burn spell—especially if I have a decent chance of disrupting metalcraft.
Is it worth it to Shatter, Revoke Existence or Grasp of Darkness a turn-two mana Myr? Hell no! Or, at least, not unless you have a very good reason ...
Given how many mana sources (lands plus mana Myr) people play in this format, the chance that you will actually be able to cripple your opponent by killing his or her mana Myr is pretty unlikely, even if he or she is only running fifteen lands!
So, if your opponent misses his or her third land drop, or you have a blazing fast (or cripplingly slow) start, then by all means Galvanic Blast that mana Myr. But don't think that you will be able to steal many free wins by simply killing your opponent's mana Myr.
However, even if it isn't always correct to, there are some situations and some cards that make killing your mana Myr very profitable. And you will need to adjust your play accordingly if you want to take advantage / minimize the effectiveness of this.
I was playing a match during Day One of Grand Prix–Nashville (which featured Sealed Deck) and in the first game my opponent played two Arc Trails, a Contagion Clasp, and two Galvanic Blasts against me. I was able to win on the back of some very large creatures (who stood particularly tall against my opponent's many 1- to 2-damage burn spells). Then it was time to sideboard.
I had misbuilt my deck slightly, but that wasn't what I was concerned with during sideboarding. I wanted to blank (or at least minimize the effectiveness) of my opponent's many cheap, high-quality burn spells.
So what did I do?
I boarded out my seven 1- and 2-toughness creatures, including three on-color mana Myr for my seventeenth and eighteenth lands (remember, you can only get away with fifteen to sixteen lands in your deck when it's loaded up with mana Myr) and five other 3+ toughness creatures.
While my opponent definitely gathered that I took out some of my little creatures pretty early on in the second game, it took him a good amount of time to realize that I was actually playing a deck with only a couple (if any) 1- to 2-toughness creatures. And by the time he realized that he would need to use two of his removal spells to kill one of my creatures, it was already too late for him to do so effectively.
The fact that you have so many playable artifacts in every Sealed pool allows for these types of big, if not particularly dramatic, transformations.
But even if you can't make this big of a switch (perhaps you are playing in a draft where you don't have that many 3+ toughness creatures in your sideboard) you can still adjust your play to make it difficult for your opponent to blow you out with Arc Trail.
Yes, Arc Trail is a very good card, but there's no reason why you have to resign yourself to the fate of getting blown out by it.
This will sometimes require you to make some pretty funky-looking plays, such as not playing your mana Myr on turn two. Or not playing your Chrome Steed off of your mana Myr on turn three and instead playing a couple of pieces of cheap Equipment to ensure that you will have metalcraft when your Chrome Steed comes down the next turn.
So while your mana Myr can sometimes be one of your greatest assets, be aware that they can sometimes become a huge liability. If you recognize when they are a liability for you, you can slow play some of your cards, or even board out some of your mana Myr entirely for extra lands in order to ensure that your opponent will not catch you with your pants down.