"It's SEA MAN!"
A little foray into Tropical Merfolk I started post Modern Horizons, deciding that while mono-blue had advantages against Blood Moon I wanted access to Kumena's Speaker. This was one of the best one-drops Merfolk had for a long while but I've dropped them and Cursecatcher in favour of Merfolk Windrobber and Tide Shaper as flyers were something the deck was sorely lacking. The mill is occasionally relevant too! Enough people play islands now that the Shapers are often 2/2s for one anyway, and have the upside of not needing to mainboard any Spreading Seas (the tempo loss in playing that instead of a body having been fatal to me more than once). When I tried Rishadan Dockhand I found it too slow for me and didn't mesh with the aggro plan of the deck, but I may reconsider now we have Deeproot Pilgrimage.
Moving up the chain and as with most fish-folk builds we're running a hefty lord package, most of them at a very accessible 2CMC, plus a couple of utility creatures. Merfolk Trickster is an excellent card all round: the floor is that you can feign countermagic by not tapping out but still have a flash threat ready to attack next turn, while the ceiling is winning you the game by tapping their only blocker or turning off an ability. Silvergill Adept just isn't good enough any longer and neither is Kumena, Tyrant of Orazca, who is waiting to become a third Svyelun of Sea and Sky for a little more consistency. I still like Merrow Reejerery enough to keep two copies, even if part of the reason is simply having a critical mass of 3-drops to justify ticking the Vials up. New star Tishana's Tidebinder is presently only a two-of, but I fully expect that number to increase given how many potential applications there are for a Stifle on legs while more flash helps keep the deck unpredictable even without Vials. Force of Negation was a strong addition to the deck as a less mana-intensive alternate to Cryptic Command, especially as Vials mean that eventually we can just pay the casting cost and still keep the threats coming. Noncreature is of course a drawback but it still helps us deal with the wraths, spell-based combo and target removal cards which are most problematic for the deck. I used to have Dismember in the mainboard but found it didn't stand up to bigger lads like Murktides or Titans, while spending four life to kill a Ragavan didn't feel like a good rate given how unlikely it is he will hit anything from this deck his controller might actually want to play.
Mana base is about what you'd expect, if I could afford it I might consider more copies of Cavern of Souls but considering the hostility of the format to creatures making them uncounterable isn't a big deal compared to keeping them alive. The channel lands are great and I've found room for all four copies of Mutavault, which elsewhere seems to have fallen from favour a little bit but I still really rate with Vials and lords.
The sideboard packs a couple of Collector Ouphes, which have applications against a variety of decks, plus some Dismembers and green protection spells. Grafdigger's Cages are decent insurance against Collected Company, Kroxa and the inevitable resurgence of Dredge. Veil of Summer is just good, not much to say here except that perhaps Mystical Dispute, Counterspell or Dismembers three and four could be better depending on meta? The empty slots are for a playset of Subtlety in case we come up against a deck that requires us to pivot harder into control.
