The Shimmersea Fae are a difficult deck to master. There are many ways it can lose economy, and only a few they can gain it. Though they are primarily an aggro deck, irresponsible economic play can quickly destroy their chances of winning.
That said, their path to victory usually requires crunching their units into the opposing player's side. They have tools to establish the crunch (like Scouts and High Tide), and tools to win tradeoffs once in the crunch (like Swarms and Spearhead). Not only that, Nymira is rewarded for this endeavour with a recurring Spearhead.
Signature Combos
1) Scout/Swarm: This uses a Scout's Call Reinforcements ability to summon during the attack phase to draw a Swarm, which has an extra attack when summoned. You can use the Scout itself to summon the Swarm on, or any other unit.
- as an assassination tool, usually allowing for 3 attacks and 5-6 wounds from a single direction
- as a recursion tool, to recover wounded units to your hand.
One noteworthy thing about this combo is that it can't be telegraphed - the Oracle's ability Peer is capable of adding extra magic where needed to make it happen.
2) Champ/Spearhead: With her primary ability (Ebb and Flow), Nymira is the strongest melee summoner. Spearhead makes her even more dangerous. Diagonal attacks are generally strong, because she can both pierce enemy cover, and attack from her own cover. Typically, maximizing this combo is the focal point of an SF victory - but it's tricky to execute successfully.
Other Main Combos
3) Champ/Tidebreaker: A champ on the board turns your Tidebreakers into a 1-cost, 3 life/3 melee unit. That's a significant value add in a deck that needs value. That champ could also have only 1 life left, and be hiding in the corner - it just needs to be on the board.
4) High Tide: It has an obvious use as an aggro tool. But often, High Tide is worth playing just to activate Nym's boost power early. That way she can come out swinging on her first attack. On the flip side, when she retreats, she can use the extra accumulated boost to heal herself from safety. The fact is, this deck is stingy on boost generation and High Tide is usually the only way to get any extra boost. Don't forget double High Tide either, as it can change the shape of a game - For example, Nymira moving four spaces and hitting a diagonal fifth space with 4 Melee Dice.
5) Luminous Scout/Gate: Unless the unit is a Swarm, a Scout always needs a Gate to summon off of.
- it can increase damage down a single lane
- it can place a blocker to defend a vulnerable target
- it can steal/protect freshly opened summoning spots
6) Oracle/Swarm: The Swarm tradeoff is expensive when summoning it over any unit that has a magic cost - except the oracle. Using the Oracle this way can lead to multiple Peers in the same turn - which can promote deck flow, or generate extra magic when needed.
How to destroy your Econ with Aggro
1) Swarm: Has the base stats of a 1-cost unit, but costs 2 magic. On its own, it therefore costs 1 magic to do an extra 2melee attack. That isn't a phenomenal economic tradeoff. That said, if you use the Swarm for anything other than this, it is a dangerous waste of magic.
2) Scout/Swarm: Probably the easiest way to destroy your econ. It might seem tempting to summon a scout, move up, attack with it, then drop a swarm on it. This does an average of about 5 wounds. Since a swarm's base stats are typical of most 1c units, you have effectively spent 2 magic to get 3 extra wounds - That is not an efficient tradeoff. There are good times to use it of course, but avoid using it unless you have a high value target.
3) Peer: The Oracle's power is useful to improve deck flow, but burning cards for magic tends to be a net loss. It is generally better to keep the cards in your hand, as long as you can maintain sufficient momentum the following turn.
4) Rebuke: This Aggro tool has its uses, but it is far from a good tradeoff. Remember that you don't just pay the magic, but you lose the inherent cost of the card itself. The way it works out, Rebuke is like paying the summoning cost, plus 1 magic, just to give your opponent's card back to them.
5) High Tide: A 1-cost event is often more expensive than it seems. You can look at it as a net loss of 2 magic (since a card always has the value of turning it into a magic). Even though it often makes sense to get Nymira the extra boost early, it still is a lot to pay for 1 boost.
How to protect your Econ
1) Twins: Enara and Lyra Deepwater are your main econ-saving tools. You can usually get each of them back at least once in a game. And at only 2c, they are also better than most 2c units, especially when considering their AV boosting effect on Tidebreakers.
2) Nymira Shoalsong herself: In any game, exposing your summoner to aggro equals economic relief. And Nymira is better suited than most summoners to stay busy and draw aggro. With her boost attack and Spearhead, she can both threaten, and attack while protected. On top of that, she can use excess boost to heal on inactive turns.
3) Twins/Tidebreakers: A 1-cost 3 life/3 melee unit is better than your average 1-cost unit, and not quite as good as your average 2c unit. Regardless, this combo adds meaningful value, and Nymira needs all the value she can get.
4) Scout/Gate blocker: Your Scouts are valuable, so their power can protect them by shielding them with weaker and more expendable units like oracles, Tidebreakers, or even more ideally, either of the Twins. You probably don't need to play all 5 Scouts - but you should protect the Scouts you have on the board, because a lot of Nym's game is generated from their Call ability.
5) Scout/Swarm Recursion: This is when the Scout's power is used not simply to assassinate, but to recover weakened units. Recovering a weakened champ that would've died the following turn is a significant bonus. If that champ is Coralis, even better.
How to protect your Econ... with Aggro
1) Spearhead/Champ: Most players will naturally want to chase recurring Spearhead as much as possible. Many probably assume that recurring Spearhead as much as possible is the key to an SF victory. They wouldn't be wrong, but I will only say this - You probably don't need to recur both. When you look at Spearhead and what it does, there are situations when it is worth a single use. Otherwise though, Nymira will gain economy quickly the longer she can hold onto a Spearhead.
2) Scout-Gate-High Tide: This combo feeds into recurring Spearhead. You drop a deep gate into enemy territory, and use the scout to summon units on it in the same turn. That helps her gain crucial traction.
Some comments about individual cards
1) Coralis Undertow: Not a great statline for a unit that tends to expose itself. But his power is sneaky good. And he can be highly oppressive when the board is tilted in Nym's favour. With Swarm's help, he can also be recurred once he has taken damage. One combo not mentioned is using a weakened Coralis to push itself forward, then dropping a Swarm on it to attack a second unit.
2) Oracles: I like the utility they add. They are not only good for improving deck flow, but they are also good targets for Swarms. For that reason, they should also threaten your opponent every time they are the board. They also aren't bad to burn for magic either, especially when you have enough units on the board already.
3) Tidebreakers: Don't be afraid to use them even without a champ on the board. They are decently serviceable 1c units that won't ding your economy too badly.
4) Swarms: Don't be afraid to burn them when there isn't an apparent or potential use. One or two Swarm combos will make a potentially useful champ impossible to summon.
5) Twins: Never, ever burn them.
6) High Tide: You should probably play at least one in a game, unless you have Coralis on deck and you need the magic.
7) Nymira Shoalsong: Most summoners have to be protected at all costs. Nymira can absorb a little aggro, but not a lot. 9 life is fine, 6 life is time to be careful, 3 life is big trouble.
8) Wade In: Basically useless when your units are Scouts and Oracles. But it is actually often difficult to destroy even a 3-life unit with a single attack. Some decks have the tools, some don't. So anything 3-life and up will usually survive a turn where Wade In is played. Then of course, they can be recurred the following turn with a Swarm.
In the defensive zone
Many players recognize that Nymira Shoalsong is stronger on their side of the board. When it isn't possible to establish a strong board presence, Nymira needs to rely on winning tradeoffs in her end. This requires careful attention to play, but the fact is, she has some tools to hold her own economically. I have outlasted my opponent in games I thought I couldn't win.
In other words, there isn't any major urgency to establish your board presence in the opponent's end early. You can bide your time and wait for the right moment.
Final Thoughts
Peer, Dredge, Ambush and Swarm all create conditions where you can't take your turn back. As if this deck wasn't hard enough to use. I still make mistakes that I can't take back, and probably always will. But there's no avoiding it - just plan your turns carefully and you'll be alright.