I've started writing this article many times. For a long time, I put it off because no one was interested. Recently however, Merfolk has been putting up results, including winning a Grand Prix. What I want to accomplish in writing this is explain why the deck is good, what cards are important in certain matchups, and the basic strategy for playing it.
I've played a bunch of Merfolk in my life in just about every format. Modern is the youngest of all formats, but I've probably played more games with Fish there than any other format. The power level of Merfolk has remained about the same for the duration of the format, but the power level of the rest of the format has shifted to where now its no longer strictly a tier 2 option, and might even be tier 1.
First things first: Modern Merfolk is not a "Fish" deck. By this I mean that it is not trying to resolve one or two creatures and attack while using countermagic to stall the game until the opponent is dead. It is not an "Aggro-Control" deck, or however you want to describe the "Tempo" "Delver" archetypes that no one can agree on a name for. Merfolk in Modern is pure Aggro. In a lot of ways, it's like White Weenie, but without the hate creatures, or Zoo without the burn spells. I know this doesn't sound impressive, and it really isn't, but the deck does win.
Why is Merfolk better than other aggressive strategies? First of all, almost all of your threats are interchangeable. Three or more different anthem creatures in the deck is maximum redundancy, making the opponents removal spells less effective. Secondly, the deck has velocity / card advantage built in with Silvergil Adept (and Spreading Seas to a lesser extent). Thirdly, it uses Aether Vial which can lead to some of the best draws available to any deck in the format. It also has four mutavaults, which bring the threat density to a very high level. Finally, the manabase is pain free, which is a surprisingly relevant upside in Modern.
The core of the deck:
4 Mutavault
4 Aether Vial
4 Silvergil Adept
4 Lord of Atlantis
4 Master of the Pearl Trident
Mutavault is a land that also is a free 4/4 creature. Its the best card in the deck. I try to aggressively attack with it on turn two when I start with turn one Aether Vial. The mana you lose from not playing a spell on turn two will be easily made up when Vial ticks up higher, and getting free points of damage in is very important for a deck without reach.
Aether Vial is the next best card in the deck. You keep most every hand that has a land and a Vial. It counts pretty much as one land for deck construction purposes, but generates 4 to 8+ mana a game. The primary way to win with the deck is to play multiple creatures in a single turn, and it is the easiest way to achieve that.
Silvergil Adept is the best Merfolk, and thus next on the power rankings. It gives you the ability to pressure the opponent without committing all your resources to the board. It digs for the cards you need to have in the matchup. You can cast it with Mutavault mana. It's great and you should never cut it.
The eight two mana lords are what gives the deck consistency. Combined with Spreading Seas they can make your team unblockable. Also, the strength of Snapcaster Mage in the format right now means you will have incidental islandwalk fairly frequently.
The next group of cards:
4 Merrow Reejery
4 Spreading Seas
4 Cursecatcher
I think Merrow Reejery is almost good enough to be in the first tier. It allows for some crazy explosive starts, even without Aether Vial. In some matchups, it can be slightly too expensive and I might side it out, so it doesn't quite make the top tier, but I would always start four in the main deck.
Spreading Seas is very hit and miss. Sometimes its the best card in a given matchup. Other times it just cycles at sorcery speed. But when its good its great, and that is why you play four in the main deck. Green decks like Jund, Abzan, and Naya sometimes don't run enough actual shock land duals to recover from a well placed Spreading Seas. This limits them to only play one spell a turn, and buys you enough time to steal a victory. It is also very important versus Urzatron decks.
Cursecatcher is the classic Merfolk one-drop, and in my opinion still the best. The rise of Kologhan's Command as a premiere removal spell makes it better than Cosi's Trickster or Tideshaper Mystic. You need at least four one-drops in the deck since you don't have an abundance of turn one plays.
The rest of the deck includes cards from this category:
Harbinger of Tides
Master of Waves
Tidebinder Mage
Phantasmal Image
Kira, Great Glass-Spinner
Vapor Snag
Dismember
Random Countermagic
Random Blue Legends
21st and 22nd lands
Maindecking SB Cards
Harbinger of Tides is great. It's awesome with Merrow Reejery. The people who say it isn't great probably don't like Reejery. I will probably always play at least three.
Master of Waves is not necessary to the deck. I know it seems like the rise in success of Merfolk has corresponded with the rise in play of this card and it's strength against the popular decks like Grixis and Jund, but it is not essential. I think it is a reasonable card to play in order to put away games faster, but a lot of times in my experience it has just been win more. Putting it in your deck has some significant drawbacks in the way you play, as you are incentivized to tick up your vials past two and three, sometimes stranding other creatures in your hand you could have otherwise played. It does work well with Spreading Seas, and can swing the tougher aggro matchups in your favor. I think because playing any number of these puts you in situations where you tick up vial at a risk, you should play more of them if you play them at all. I would avoid only playing one or two, and try to fit all four in if I were to play the card.
Tidebinder Mage is great when it works, but obviously not great when it doesn't. I always feel like I "get lucky" to have it work game 1, since I'm only playing a couple in the main deck and have to get the right matchup. Unlike Harbinger of the Tides, it allows your opponent to get the mana back by killing the Tidebinder, where Harbinger always sets them back that mana. Tidebinder is better when trying to break through, but Harbinger is better when racing. Harbinger is also better versus non-red and non-green guys (obviously). I prefer Harbinger, but sometimes you might want both.
Phantasmal Image is a lot of ways the opposite of Master of Waves. It keeps your Vials on two, but still increases your clock. It also lets you make some interesting plays by copying the opponents creatures. However it is much worse vs grindier matchups, where the best it can do is copy an adept to avoid risk of being blown out later. In some metagames its probably right to play four of these, but usually it is too much of a liability if you aren't trying to be as fast as possible.
Kira, Great Glass-Spinner is a great card vs UR and Grixis. It can really throw off the opponents game plan when they are waiting with removal for your lord and instead you play her. She also works great with Spellskite out of the sideboard. I've had great success with her in the main deck to be "pre-boarded" against grixis and other UR decks.
Vapor Snag and Dismember are really the best options for removal in the mono color build. Dismember is nice because it can be another turn one play, but a much worse top deck in the mid to late game racing situation. Vapor Snag is useful in saving your own guys, acting as a pseudo counterspell that can also clear the path for blockers, but it is much worse at answering opponents one and two mana creatures.
Various Counterspells are all pretty bad in the main deck. Remand and other two mana spells are only good in draws that involve Aether Vial. Picking the right one mana spell will just give you frustration when you have the wrong one, and none of them deal with creatures. Spell Pierce is fine, until you play against Tron. Dispel is fine, until you play against Liliana. The best strategy is to play some in the SB that are the best for the matchups you expect, then use them games two and three.
Various Blue Legends include Sygg, River Cutthroat, Thassa God of the Sea, Vendilion Clique, and Venser Shaper Savant. Sygg is cute, but no longer strong enough compared with the other main deck creatures. Thassa is reasonable, helps you to mitigate flood and can occasionally attack. You can also vial her in, but never want to draw two. Venser and Clique don't do enough vs the field to warrant the inclusion in the main deck but could be reasonable sideboard cards. Playing with any makes Minamo actually relevant sometimes, but thats not enough to require it. Minamo still good enough vs Choke to make the cut.
I like to play 21 lands. Most builds play 20 lands. If you play 22 lands, you can play a couple of colorless lands in addition to Mutavault like Tectonic Edge or Ghost Quarter. My logic for playing 21 lands: I am going to keep every one-land hand with Aether Vial, and I want to be better off in those situations at drawing the second land. Some lists run four or more lands in the sideboard to bring in when you side out Aether Vial or you just want more mana to hold up countermagic. It is a good plan but one that takes up a lot of spots that you must sacrifice some matchups (usually no Hurkyll's Recall for the Robots matchup).
Maindecking Sideboard cards like Spellskite, Relic of Progenitus, Pithing Needle, or others can be a good way to increase the total number of sideboard cards you can play. I would make sure you have all your plans covered though, you don't want to get stuck with dead cards in the deck after sideboard.
Cards in other colors:
Path to Exile
Sygg, River Guide
Stony Silence
Collected Company
White is the easiest second color to play. You get both Seachrome Coast and Wanderwine Hub which are pain-free sources of both colors. You also get Path to Exile, a real removal spell that can let you play a more traditional game of magic. Stony Silence in the board is a much stronger card vs Affinity, Tron, and Lantern than Hurkyll's Recall, but comes at the cost of having to side out Aether Vial. Sygg River Guide is good enough to always play one, especially with Aether Vial. Other white SB options like Meddling Mage, Burrenton Forge Tender or other anti-red cards, and Detention Sphere can help you versus the wide variety of decks that exist on the fringe of modern. Not having as many islands helps in the mirror. The biggest drawback is your fourth land not always being untapped when you want to activate two Mutavaults, and getting stuck with white cards in your hand and not being able to cast them. I played a UW version at GP OKC that I was very happy with despite not making day two. I punted key games in two matches that I should have easily won.
I've tried just about every color combination of Merfolk, including green for Collected Company, black for Inquisition of Kozilek and Dark Confidant, and red for Lightning Bolt and Blood Moon. The price you pay on the mana base is just never justifiable for the gains you make. Maybe if a good two color Merfolk is printed you can re-evaluate.
Sideboard Cards
Spellskite
Swan Song / Spell Pierce / Dispel
Remand / Mana Leak / Unified Will / Delay
Hurkyll's Recall
Hibernation
Pithing Needle / Phyrexian Revoker
Relic of Progenitus
More Creatures
Lands
I like Spellskite a lot as a sideboard card because it is great in the Bogles and Infect matchups, as well as being good vs Snapcaster + Lightning Bolt decks at protected your guys, especially with Aether Vial and Kira. It also protects from Splinter Twin combo.
Hurkyll's Recall should likely be a four of in your sideboard. It is good enough to beat affinity, and you really don't need too many cards for other matchups in my opinion.
Hibernation is similar to Hurkyll's Recall, but Elves is not as popular as affinity.
The countermagic and other cards really depends on what you are comfortable with. I like Swan Song a lot because it is cheap enough to come in vs URx and actually good vs Scapeshift, but Unified Will is better versus something like Tron and random combo. Dispel is only good at protecting your team, but very good at that. Spell Pierce is probably best in an unknown metagame.
You can play cards like Tidebinder Mage in the sideboard. Some matchups you would rather have it that Hibernation, so I like to run a split. Revoker and Needle are both good versus a variety of decks, but not great against anything specific.
I covered the land SB strategy above, but included it in the list for completeness. It's a good strategy, but one that makes your deck better vs the sideboard of the popular decks and ignores decks that are bad matchups. If that's a SB style you agree with, it's worth considering.
How to Play the Deck;
The deck doesn't play like a traditional Fish deck, but also not like a traditional Aggro deck either. It's not important to use all your mana every turn, or to get an early presence. Many decks are prepared for this, and running your lord out on turn two into lightning bolt, only to have your turn three play get killed by snapcaster bolt will not be a successful strategy.
When you have Aether Vial, sometimes it is best to just wait until the end of their turn to put things into play despite the fact you can do more damage on your turn. The goal is to make it difficult for your opponent to disrupt you. Spreading Seas is a great turn two play instead of getting a creature killed on curve for your opponent. Also waiting to play your guys will let you see more cards and have a better critical mass of creatures.
I keep any one land hand with Aether Vial. I like to play Vial with Mutavault mana and attack with Mutavault on turn two.
I side out Spreading Seas against any deck that already has islands. Playing Spreading Seas before you play your threats is also a good plan, Sometimes you can steal wins by mana screwing your opponent. However against decks that are more aggressive than you, you probably don't have time to play Seas. Sometimes your best plan vs Bogles is to hope they kept the one lander though.
Cursecatcher gets sided out fairly often. When people have sweepers it just gets caught up in the wash, and it's not actually good against many decks.
The biggest advice is to just be patient. Most decks don't play the cards necessary to break up a board of 3+ lords, so try to get that to happen. You don't have to attack into Deceiver Exarch mana.
The Decklist:
I would suggest starting with Paul Rietzl's list from GP OKC to start. It is very streamlined and aggressive without much cute stuff for interacting.
Anyway, that's all for now. I'll try to update this in the future, maybe elaborate on some spots or add more cards to discuss. If you have any questions post in the comments or tweet at me @ceciliajupe.
