Mirrodin brings us the interesting affinity mechanic - but is this mechanic good enough to build a viable type II deck around? I believe it is. Affinity decks are not unlike Madness decks; both use undercosted creatures backed up by counterspells and card drawing to win.

Because affinity is a mechanic that reduces casting cost, we need to build an aggressive deck in order to use the tempo advantage it provides. (This may seem redundant, but I have seen a lot of people in forums making an effort to build affinity-based control decks.) However, an aggressive deck doesn't mean mindless bashing, so we will also need some cards that interfere with the opponent's plans in order to win.

So the best version is an aggro-control deck.

Sadly, affinity has one inherent weakness: Inconsistency. It relies on other cards to be already in play for it to work. The deck needs to set up a sort of"chain" to get going. It is very tempting to try and make the deck as fast as possible by using cards like Ornithopter and the X of Chiss-Goria artifacts. While a deck built like this will get insane draws from time to time, it will also lose a lot because it sacrifices too much consistency to gain tempo.

The deck becomes even more inconsistent if a lot of non-blue cards (or cards that require multiple blue mana), are included. Cards like Megatog, Shrapnel Blast, Vedalken Archmage, and Pyrite Spellbomb are attractive, but they'll either make your deck more inconsistent or will require you to run more mana sources than would otherwise be needed. Add to this that we have creatures available that are more than capable of dealing with blockers and killing the opponent on their own, and you'll understand why I run only blue and colorless spells in the maindeck. I have also kept the number of cards that require two blue mana to a minimum.

My sideboard includes black spells and Assert Authorities because they are simply needed.

After some fifty hours of playtesting I have come to the following build:

4 Frogmite
4 Myr Enforcer
4 Lodestone Myr
3 Broodstar
4 Thirst for Knowledge
4 Thoughtcast
4 Mana Leak
4 Welding Jar
4 Aether Spellbomb
3 Lightning Greaves
4 Talisman of Dominance
4 Seat of the Synod
4 Vault of Whispers
4 Ancient Den/Great Furnace/Tree of Tales
4 Glimmervoid
2 Island

Sideboard:
4 Persecute
4 Infest
4 Annul
3 Assert Authority

This deck has fifteen creatures - which may not seem like a lot, but because it also has eight spells that draw cards you will rarely run out of them. Seven of these creatures (namely, Lodestone Myr and Broodstar) can easily win the game for you in one or two turns.

Most builds I have seen on forums run only twelve creatures, but I strongly believe this is too little because affinity decks tend to be so inconsistent.

There are a lot of creatures that are worth considering for this deck, so I'll explain why the following ones made the cut, while others didn't.

Frogmite
This may not look like much, but it helps to get the deck going. Just like any"bear," it can trade in combat or deal some damage to a player, so it is never useless. The first one can generally come down on turn 2.

Myr Enforcer
The"workhorse" of this deck, it alone presents a five-turn clock and weenie decks will often have to make two-for-one trades to get rid of it. The first one can typically be played on turn 3.

Lodestone Myr
This thing is very cheap for its potential size and has trample to boot - add in its synergy with Aether Spellbomb, Welding Jar, and Lightning Greaves and we have a winner.

Broodstar
It flies and is more often than not big and cheap. Unfortunately it also has two blue mana in its cost and usually doesn't come down till turn 5, so we only need three of them.

Ornithopter, Steel Wall
This is an aggressive deck so the last thing we need are creatures that can't damage the opponent. Steel Wall is a passive defense against Goblins and White Weenie; I'd rather run the aggressive Infest.

Somber Hoverguard
Too fragile for its cost. Further weakened because it is not an artifact.

Vedalken Archmage
While it seems perfect for this deck, testing revealed it to be too slow and fragile. If Lightning Greaves equipped at instant speed, this might have been a good choice - but it doesn't and it's not. Not to mention that its double blue cost can also be a problem.

Lumengrid Augur
Although it is loads of fun, it is just as slow and easily killed as Vedalken Archmage.

Atog, Megatog
These creatures counteract the affinity mechanic and require red mana, so this deck is not their place.

Now that we have established a creature base we need some card-draw, to increase consistency and prevent the deck from running out of steam. Of course, I use four Thoughtcasts; it rarely costs more than one blue mana in this deck. The next inclusion is Thirst for Knowledge, it's just three mana and you will almost always discard an artifact instead of two cards.

Because of its low cost, Thirst for Knowledge beats Rush of Knowledge and Vedalken Archmage, even though these can gain more card advantage. Rush of Knowledge needs Myr Enforcer or Broodstar to be good, just like Vedalken Archmage needs two blue mana as well as several artifacts to be good.

Thoughtcast and Thirst for Knowledge help us get mana or creatures when we do not have enough.

Some people in forums have suggested Howling Mine, because of its synergy with Lodestone Myr. During testing I found Howling Mine to be ineffective; without Lodestone Myr it is terrible card disadvantage, as it benefits your opponent more than yourself. And if you do have a Lodestone Myr in play for two turns, you'll almost certainly win, regardless of whether or not you have a Howling Mine in play as well.

In addition to card drawing, this deck needs some disruption to stay alive, particularly against mass removal. The question is how much disruption and which cards? I believe this deck can get away with maindecking only the most efficient counter in type II: Mana Leak. You'll mostly need to counter something like that one critical Wrath of God or Siege-Gang Commander, and Mana Leak does that job just fine. I don't have to tell you why it's good, so instead I'll tell you why the rest are inferior.

Mirrodin brings us Override and Assert Authority. Override doesn't do much more than Mana Leak in the early- to mid-game, which is when this deck plans to win, but it does cost one more colorless mana.

Assert Authority needs four artifacts in play to be reasonably costed, and then it still needs two blue mana, which this deck does not always have to spare. However, I need it in the sideboard against W/x control decks, because it is generally the cheapest hard counter in this deck and it stops Eternal Dragon. From older sets we have Rewind and Discombubulate, these are just too expensive.

Also there's Dispersal Shield, which faces the same problem that Rush of Knowledge does; it needs either Myr Enforcer or Broodstar in play.

Annul is very good against some decks, and better than Stifle against Oblivion Stone, so it is in the sideboard.

The rest of the decks consists of its mana base - more on that later - and some versatile artifacts. Welding Jar is one of these artifacts, and it is the card I replaced Chrome Mox with during my testing. Welding Jar speeds the deck up, but it can also regenerate our artifacts when necessary - something Chrome Mox can't do. Having one or two Welding Jars in play makes things a lot harder for your opponents, especially if they rely on cards like Oblivion Stone and Akroma's Vengeance to deal with your creatures.

Aether Spellbomb can bounce a blocker, save one of your own creatures, or you can sacrifice it to dig for something you need. So basically, it is never a dead draw.

Last to be included is Lightning Greaves; this wonderful equipment can win games because it makes the deck a lot faster as well as more resilient to targeted removal.

Lightning Greaves is the only equipment I run, as most of the creatures are already big enough without equipment that increases their power and/or toughness.

The mana base is largely made up of even more artifacts in order to maximize affinity. The only artifact that isn't also a land is Talisman of Dominance. This card is great in this deck because it is"free" if you play it before spells that have affinity, and it can provide us with the black mana we need for some of our sideboard cards.

Not using these would mean having to include the painful City of Brass, which has no synergy with affinity cards and Lodestone Myr. Because the deck includes four Talismans, it can afford to run just eighteen land. Twelve of these lands are artifact lands, eight of them are relevant to our colors; I do believe an affinity deck needs to run at least twelve artifact lands to have good tempo.

Four Glimmervoids are a logical inclusion to help us get the color of mana we need; add that to the two, and we'll reliably have enough blue mana.

I have tested Chrome Mox a lot but I found it does little to nothing in this deck, as the only card I could sometimes afford to imprint was Broodstar. This makes me wonder: If Chrome Mox isn't good enough in a deck where after affinity it often reads:"Tap: Add 1U to your mana pool," what deck is it good enough in?

Now that I have explained my card choices for the mainboard, I'll move on to the sideboard, and the matchups it has been designed for. While I have chosen to keep the sideboard strictly black and blue, other colors might be just as viable. Red offers Pyroclasm. White has Second Sunrise and Sacred Ground and green has Naturalize. Sideboards are often about personal preferences and the metagame you expect to see, so it is not set in stone.

I have chosen black because it has excellent cards against both control and weenie decks.

Persecute
This card is especially good against mono-colored control decks like Mono Black Control and Mono White Control. It can be played on turn 3 if we have a Talisman in Play.

Infest
Needed against decks that try to overrun us with weenies, like the various Goblin and White Weenie decks.

Annul
Annul helps against decks that have lots of artifacts or enchantments, like other affinity decks and Mono Black Control.

Assert Authority
This is our best option against control decks that use more than one color, like U/W control.

It's matchup time!

Mono Black Control
This deck will be played a lot; fortunately, this is not a bad matchup for us. Most of their removal is inefficient; Smother does nothing, Terror can only target Broodstar, Infest can only kill Frogmite, and Consume Spirit is stopped by Lightning Greaves.

That leaves Oblivion Stone to worry about. While Oblivion Stone is bad for us, it is not as bad as Wrath of God or Akroma's Vengeance because we can use Welding Jar to regenerate and Oblivion Stone does not kill our artifact lands. So you should be able to win game one.

However, some versions run Grid Monitor, Dark Banishing, and/or Barter in Blood, which makes it much harder for us. Other people will run some of these cards in their sideboard, so be ready for them. Fortunately, we also have excellent sideboard cards against them.

Persecute can be played as early as turn 3 and will wreck their hand and often their game, so add four. To combat Oblivion Stone, Extraplanar Lens, Grid Monitor, and Phyrexian Arena, we sideboard in our four Annuls. Take out the three Broodstars because they die to Terror anyway.

Side out four Aether Spellbombs because they are of little use here, and also take out a Lightning Greaves to make room.

Overall win percentage: At least 60%.

Goblin/Goblin Bidding
The fastest deck out there provides a real challenge. This matchup mainly comes down to who has the best opening hand. If you can get one or two Myr Enforcers out quickly you'll have a good chance of winning, but sometimes they'll just outrace you. Try to counter their Siege-Gang Commanders, or Patriarch's Biddings if they run any. Your likeliest path to victory is Broodstar; they have no real answers for it. The first game is more or less equal.

Some decks run Ensnaring Bridge in their sideboard, which is very bad for us. If they don't, our chances of winning go up because we can bring in four Infests to slaughter their goblins. Take out the four Aether Spellbombs because they do not help much here.

Overall win percentage: Just above 50%.

U/W Control
This is one of our worst matchups if they've built their deck correctly. A good build runs at least four Wrath of Gods, three Akroma's Vengeances, two or three Wing Shards, and possibly some Oblivion Stones.

This deck is brutal because Akroma's Vengeance destroys everything except our Islands, and they have counterspells and card drawing to back it up. So you will struggle in game one and you will probably lose... And this is extra-bad because game one will often take a lot of time. After that, they will sideboard Annul in against you, and some Wing Shards and/or Akroma's Vengeance if they have extras.

Still, our chances go up a little after sideboarding because we bring in three Assert Authorities. Take out three Lightning Greaves to make room. With seven counterspells in our deck, we have a much better chance of countering their vital Wrath of God or Akroma's Vengeances and win... But their counters and mass removal will still win them the game if they resolve.

Overall win percentage: Below 40%.

White Weenie
The best versions run Bonesplitter and Glorious Anthem to enlarge their creatures, which can be a problem for us. Most decks also run eight to twelve creatures with flying, so don't count on Broodstar to get through quickly. It is very important to outrace them or counter their Glorious Anthems in order to win. Myr Enforcer and Frogmite are less effective than usual in this matchup because they have to compete with 2/2 and 4/2 (equipped) first strikers.

Some builds run Wing Shards or Wrath of Gods, so don't overextend or run into a wall of Shards. Game one is tough, and I think White Weenie has a slightly better chance. (Some decks I've seen have Akroma's Vengeances in the sideboard, so keep that in mind.)

To destroy their creatures, we board in four Infests. We add four Annuls against their Glorious Anthems, Bonesplitters, or other equipment they might run and against Worships they might board in. It is very important that you keep Glorious Anthem off the table, because it spoils our Infest plans.

To make room for all these cards, take out four Frogmites and four Welding Jars. Frogmite is worthless against White Knight and Silver Knight, and it dies to our own Infests. Welding Jar doesn't do much because we now have fewer creatures and if they have removal it won't allow regeneration. After these changes, our deck is much closer to a control deck designed to beat them, so your chances will improve a lot.

Overall win percentage: Around 60%.

Affinity
The mirror match is about who has the most luck... There isn't much strategy involved. It is mostly about who gets Broodstar out first, because it flies over the ground stalls. Sideboard the four Annuls in and hope for the best. Remove the four Welding Jars, because it matters least in Broodstar wars.

Because we have no special"tech" to give us an edge in the mirror match, our odds of winning are 50%.

Mono White Control, B/W control and R/W control (slide)
These matchups are rough because these decks run so much mass removal. They are not as hard as U/W control, though, because they have less card draw and no counterspells. Game one can swing both ways.

After sideboarding, we can bring in more counterspells and some discard to tip the scales in our favor. Their sideboard will likely be less useful than ours.

Against Mono White Control, side in four Persecutes. Remove one Aether Spellbomb and three Lightning Greaves.

Against B/W control, side in three Assert Authorities and remove three Lightning Greaves.

Against R/W control, usually Astral Slide decks, side in four Annuls, make room by removing three Lightning Greaves and an Aether Spellbomb.

Lightning Greaves is boarded out against these decks for the reason that they all run Wing Shards, which nullifies its haste benefit, and because most of their removal doesn't target.

Overall win percentage: A little over 50%.

So there you have it: I think this deck at least comes close to being tier 1 and is a viable option for the upcoming States tournaments... Especially because some people won't keep this deck in mind when building their decks and sideboard.