BASICS
A merfolk deck that focuses on creatures being unblockable and having low cost. So it starts out quick and small but gets quickly out of hand with counters. About half the creatures are naturally unblockable but when you put in Herald of Secret Streams every thing with a +1/+1 counter becomes unblockable. The final piece of combo is Song of Freyalise meant for that last push to give everything a +1/+1 counter, vigilance, trample, indestructible and with Herald of Secret Streams, unblockable.
STRATEGY
OFFENSE
The big question becomes what to play when. In play testing I've found that it's best to have a hand with at least one Island and one Forest. If you get a regular land and a Hinterland Harbor play the regular land first so you get that Harbor untapped when it comes out.
After that it depends on which cards you get in your hand. Best result is Mist-Cloaked Herald on Turn 1. Then on turn 2 it's best to get either the Jade Bearer or Deeproot Elite. Always keep in mind that you should put them down in the order that gives you the most counters. For example play Deeproot Elite first so when you cast Jade Bearer they will both get +1/+1 counters.
River Sneak can be played similar to Mist-Cloaked Herald it has no real prerequisites and serves as a 1/1 unblockable Merfolk. If you put it out first in a turn it can get +1/+1 until end of turn. Hopefully you'll either get Herald, Bearer, or Sneak in your opening hand.
After turn 3 the strategy opens up with the focus on protecting your unblockable pieces, putting counters on them, and swinging every turn. Included in this is the River Heralds' Boon which will give you two +1/+1 counters for one and a green. Great for defense but also for pumping.
Your early hammers are going to be River Sneak and Mist-Cloaked Herald. When ever you can gain counters, put them on these unblockable creatures. This does leave you weak to spot removal like Cast Down but hopefully your counterspells will block that (more on that later).
Deeper in you have some options. Your power pieces are Kopala, Warden of Waves and Kumena, Tyrant of Orazca and Merfolk Mistbender. The first 2 are legendaries so there's only 2 of each in the deck.
Kopala, Warden of Waves grants you a defense bonus by making abilities and spells that target your merfolk cost 2 extra. Be cautious of this though as it may draw more aggro to you as a player. So that Abrade or Lightning Bolt may start coming at you instead. See more about that under the DEFENSE section.
Kumena, Tyrant of Orazca is more complicated but very powerful. He has three activated powers all running on creature tapping. The first power allows you to tap 1 merfolk to make him unblockable. The second sees you tapping 3 untapped merfolk you control to draw a card. And the third power allows you to put +1/+1 counter on EACH merfolk you control. So do that on turn 2 of the Freyalise and get a nice set of fatties. If you get out the Herald they'll be unblockable to boot. Merfolk Mistbinder gives you a nice +1/+1 to other merfolk but spot removal can easily drop it, so I prefer counters.
You have a 4 drop unblockable with Storm Sculptor a 3/2 unblockable if things go far enough.
Forerunner of the Heralds lets you tutor for one of your Merfolk creature power pieces as well as getting a +1/+1 counter for itself every time a merfolk comes into play. If you're doing this though you're probably going to turns as it's one of the highest cost drops in the deck. Still good in a pinch to get that last piece you need.
Don't despair if you aren't getting your unblockable pieces right away. Just keep applying counters on what you have. Waiting in the wings for turn 4 is Herald of Secret Streams and Song of Freyalise. If you are feeling lucky or have a solid cast of creatures you can cast Song early if you need its mana ability. But it's best to save it for a turn or two before you cast the Herald. If you time it right, cast Herald the turn before the Song hits its third counter. When it comes back to you, you will have an unblockable board with trample, vigilance and indestructible. So theoretically you could swoop for the kill by turns 5-8. But that requires a lot of skill and more than a bit of luck on the draw. Now to the Spellbook for defense!
DEFENSE SPELLS
All the spells (except the one enchantment) are instants. There is a variety. You have counterspell with Admiral's Order which you can cast for 1 as long as you attacked that turn. You should be attacking with your unblockables whenever you can. If all that should fail, then you can fall back on three tools.
CLUTCH TOOLS
1) Merfolk Trickster - cast this on your opponents turn to eliminate activated abilities like the Siege-Gang Commander and others. It has flash so think of this as (literally) the poor man's Disallow only not as flashy or generally useful.
2) Blinding Fog - this is good for damage weenie board wipes, the Goblin Chainwhirler ETB ability and other attempts to zap any and/all of your creatures. This needs to be used in emergencies or if your unblockable pieces are still small and need some cover. It's a short term solution. It's a nice counter for creature damage.
3) Kopala, Warden of Waves - This guy is also good at protecting creatures in the early game (and against heavier hits later on) with his +2 on spells and abilities that target Merfolk, of which you have many. This again is to keep your creatures safe from Lightning Strike or an Abrade. As mentioned earlier this may draw the player a lot of direct damage hate, especially from red. So if you're playing someone with a lot of burn you may want to dip into the sideboard for some more counterspells (discussed below).
SIDEBOARD
In general this contains extra hate depending on what you're fighting. You can side in more bounce, counter, or destroy artifact/enchantment. The unique pieces though are Arcane Flight for flyer block, Shapers' Sanctuary if you run into a lot of targeting or you need card draw and Wild Onslaught if you need extra push later in the game. There is a Blink of an Eye and another Trickster if you need some bounce/ability cancel. Time of Ice is more to slow things down and it's more an oddity until I find something I like better.
CONCLUSION
The deck does require a bit of luck but most of it is about timing and order. Take your time, add your counters, attack with unblockables, and leave mana open to cover yourself. As a general rule, you want to cast your counter granting mobs first and bring your power bonus ones for later. See ya later, wizard.
NOTES ON COST:
If you don't get the Hinterland Harbors you can cut your cost by nearly 10$ and if you pass up Kumena, Tyrant of Orazca you can save another $10-15. On the plus side, everything here is Ixalan forward so it will be last quite a while if you're playing in Standard. Costs are as of 6/26/18.
