With Modern Horizons fully spoiled, brewing can get into full swing. So far, my experience has been guardedly positive. There are a lot of very interesting cards and restrained designs that should reinvigorate fringe Modern decks without upending the format. Still, other cards show frightening promise.
Brewing in the Snow
I'll kick things off with snow. Between Ice-Fang Coatl and Marit Lage's Slumber, there's a lot of incentive to make snow a central theme for decks. But I struggled to find a competent shell, failing to produce an even-publishable Temur list.
The problem with the Temur Snow lists I tried was the mana. You have to play a lot of basics to make the snow theme work. This makes the mana clunky compared to normal fetch-shock decks. Playing lots of fetchlands helps, but every fetch included is a utility land or actual land you can't play, and if I didn't have a Birds of Paradise, I couldn't hit a good curve. The longstanding problem of Temur being anemic compared to Jund was present, but it wasn't nearly as troublesome as the mana. Get the mana to work, and power can be found. Even with the surprisingly playable and necessary Arcum's Astrolabe greasing the wheel, the decks just never got going, and clunked themselves to death on mana problems.
Blood on Ice
Giving up on Coatl was difficult, but doing so paid significant dividends. Blue Moon has long been a fringe contender in Modern, and more easily accommodates the critical mass of snow permanents necessary for the payoff cards.
This list was fairly unreal against creature decks and almost nothing else. If Blood Moon didn't resolve, it didn't have the means to hang with counter-heavy control or ever disrupt a combo deck. I figured that would happen because I was building it as proof-of-concept rather than actual metagame deck, and in that role, it succeeded.
Marit Lage's Slumber is a very interesting finisher. Against control it is terrible, since they have Path to Exile and two types of Teferi to deal with the token before it attacks. It also doesn't provide the continuous card advantage of Search for Azcanta // Azcanta, the Sunken Ruin, so you'd never play Slumber in a control heavy meta. Scrying several times a turn isn't good enough in those cases. Against combo and creatures, Slumber is far better, since it threatens to win the game next turn with a massive blocker. It does take a while to fire, but in a more counter-heavy version, time would be less of an issue.
As for the snow theme, it was a bit weak, but still playable. The mana for Blue Moon has always been solid, and Prismatic Vista functions as an additional Scalding Tarn most of the time. Astrolabe proved critical to smooth out the awkwardness, and combos with Slumber to be a sorcery-speed Opt, which isn't bad. Winter's Rest is weird, but Blue Moon typically struggles against big creatures, and Rest does answer them while adding to the snow count.
Oh, The Humanity
After considerable tweaking and testing, I wouldn't end up changing anything about the Humans maindeck. I was very high on Unsettled Mariner last week, and Ranger-Captain of Eos has received some attention. While neither card was unplayable by any measure, they didn't prove themselves to be better than the current stock Humans list. Mariner would definitely make the cut in a different metagame, but it will take seismic shifts towards combo for Ranger-Captain to ever make the cut.
Mariner is phenomenal against any deck looking to trade removal spells for Humans, as predicted. Combined with Thalia, Guardian of Thraben, it is very possible to completely lock opponents out of the early game, and even when that's not possible, the two buy enough time for the rest of the team to get there. Even if they're not the nastiest threat on the board, opponent still needs to spend their limited mana on the Mariner and/or Thalia first, or they'll never be able to catch up. If Jeskai Control were the top control deck, Mariner would be at least a three-of in Humans' main. However, the control deck de jour is UW, which is more about sweepers. The other top decks are Izzet Phoenix, Tron, Humans, and Dredge, so there's little need for Mariner.
As for Ranger-Captain, the tutoring ability is okay, but not amazing. Champion of the Parish off Militia Bugler is never great, and that's realistically all Ranger-Captain finds. Tutoring is usually best used for silver bullets, and the only one that Captain can find is Burrenton Forge-Tender. Playing Eos for its stats and tutoring is asking for disappointment.
The real draw is the sacrifice ability. Stopping opponents from playing noncreature spells is, in theory, devastating against combo and control decks. Sacrificing Eos is saying "I'm going to win the game next turn." Against a combo deck, that is likely to be true, since you can only use the ability to stop them outright or after letting them use up a lot of resources but before they play their win condition. However, against control, that statement must be modified to "...if you don't also have Cryptic Command or Settle the Wreckage, I'm going to win the game next turn." The odds of that being true are far lower, and given that control is more popular than combo right now, I wouldn't play Ranger-Captain.
Siding into Danger
The sideboard is another story. Plague Engineer is just as powerful and dangerous as I imagined. I've had games where I completely lock my opponent out with multiple Engineers, and others where my Engineer backfired thanks to opposing Phantasmal Images. Given how potent Engineer is against other creature decks, I would definitely run Engineer in Humans; I'm just leery of siding it in for the mirror thanks to Image.
Of course, Engineer isn't the only potential inclusion from Horizons. If artifact decks make a resurgence, Collector Ouphe would make the cut. Stony Silence is incredibly powerful, but can't really be played with Humans' manabase. I wouldn't rely on Ouphe against Tron, because Damping Sphere is so powerful and useful against Amulet Titan. However, if there's a shift towards artifact combo, then a swap could be warranted.
The final human to discuss is Yawgmoth, Thran Physician. Protection from Humans makes him a theoretical mirror breaker. However, four mana is prohibitive. Also, sacrificing your creatures to incrementally shrink opposing creatures isn't great. Noble Hierarch may seem useless, but exalted is critical to force creatures through and/or make Yawgmoth a reasonable clock. The fact that you also have to pay life for the ability is risky, too, since often the mirror is about trading early haymaker damage until a board stall emerges. Yawgmoth wasn't terrible, but I didn't find him great, either.
Living the Life
The final deck I've been testing is the Life from the Loam engine. I call the engine itself a deck because you can build whatever you want around the engine and it is going to move. I've tried out prison, aggressive, and combo versions, and so far the best has been a combo/control version of Assault Loam.
The idea is to use Dark Confidant and Bloodbraid Elf to find the payoff cards while the unicycle lands dig for Loam. You have the most useful retrace card as disruption and lots of removal to not lose to creature rushes or Scavenging Ooze. These lists have been very hard to build, and I wouldn't actually play my shell, but their purpose was to test the viability of the Loam engine in Modern. And I'm very confidant that it is, in fact, viable.
Loaming is just as powerful today as I remember it being over a decade ago. Once the engine gets going, Loam decks never run out of cards, and will find whatever they need to win. The engine is mana-intensive, but the odds of ever missing land drops in a 28 land deck are highly unlikely. Its main issue is getting it online. Surviving long enough to actually utilize all the extra cards can be tough in Modern, and my shell is not very good against creature decks. If you dredge away any removal spells, you tend to lose to Humans. This is a solvable problem if the deck is worthwhile enough to keep refining.
But the engine isn't enough to carry the deck alone. To use a car metaphor, I'm sticking an F1 engine into a commercial subcompact; the car has all the power in the world, but it can't actually wield it. That Assault Loam and similar decks haven't worked in Modern before has as much to do with the shells themselves as the lack of unicycle lands. The decks are land-heavy, thus frequently flooding to death, and depend on a very small number of payoffs. Thus, even with the additional consistency of eight one-mana cantrips, my Loam decks typically clunk out themselves rather than grind out my opponents.
Beneath the Leaves
Engine decks usually fail when their engines never start. Loam decks are particularly prone to this failure because without Loam, the payoff cards are pretty laughable. There's a reason that Seismic Assault is never played for simple value. Between the impending London Mulligan and the unicycle lands, it will be far easier to start Loaming. The lands alone were enough to support Extended Loam.
However, Modern Loam decks have to deal with graveyard hate on a scale impossible in Extended. Back then, there was only Yixlid Jailer, Leyline of the Void, and Tormod's Crypt to contend with, and only in quantity when players remembered that Dredge existed. Relic of Progenitus, Surgical Extraction, Rest in Peace, and Scavenging Ooze are everywhere in Modern in addition to Leyline. Without the graveyard, the engine can't run and the deck fails.
All Loam decks need to do to beat Surgical is hold up a unicycler to save their Loams in response. However, Rest in Peace requires an answer. Assassin's Trophy is very good at that, but Rest would still interrupt the engine. Once you have a graveyard again, it will take at least a turn to restart the engine, and losing a turn in Modern can be fatal. In short, the Loam engine is better now than ever before, but the disruption for it is also much better, and my testing was ultimately inconclusive.
This leads me to think that if Loam wants to break out in Modern, it will need a radical redesign. Assault Loam has a very long pedigree, and I struggle to envision a deck that could utilize the Loam engine as well, but given how graveyard-hostile Modern currently is and how much more it could be, I think a new shell that attacks from multiple angles must be found.
I tried out creature-heavy Aggro Loam and it didn't work. It was between a clunky Zoo deck and bad Dredge. Countryside Crusher isn't the threat it used to be. I also tried a Bant Control deck which used the Loam engine and Courser of Kruphix instead of planeswalkers for card advantage. There, the typical control arsenal didn't work well when I was dredging Loam every turn; Snapcaster Mage and Misson Briefing weren't quite enough to make up the difference, though it was very close. I also tried a planeswalker-heavy build, and it was too clunky. If the problem of running out of answers gets fixed, then Control Loam could be a real deck.
The final thing my Loam testing suggested to me was that Wrenn and Six is overhyped. Wrenn got a lot of hype when spoiled, and it makes sense. Crucible of Worlds is a good card, and Wrenn is cheaper and does other things too, all of which are potentially useful. If nothing else, Wrenn is notable as the first clearly useful two-mana planeswalker. However, I'm always skeptical about heavily hyped cards, so I've been testing him. And I'm unimpressed.
Wrenn is a mediocre card on face. Getting back a land every turn is a good, but not great, ability; see the limited play Ramunap Excavator and Crucible receive. The former is only used to replay Ghost Quarter or Horizon Canopy in GW Valuetown, while the latter is primarily a sideboard card against land destruction. The minus one will kill mana birds, but little else, and while the emblem combines nicely with the +1, retrace has never been gamebreaking.
In a Loam deck, Wrenn is playable because he's the closest substitute to Loam available, but even then he's mediocre. Again, without Loam, the deck isn't very good, and Wrenn can at least get things moving. However, he's only a third of a Loam. Also, a lot of the value of Loam is dredging every turn to find more lands, which Wrenn can't do. Loam decks will also already have a lot of retrace cards, so the emblem is slightly superfluous. Finally, he shares Loam's vulnerability to graveyard hate. Without a graveyard, Wrenn doesn't do anything.
I've only tested Wrenn in Loam, but other players I know have tried it in various non-Loam value shells and found him underwhelming. I'm told Wrenn's generally not bad, and mana-hungry decks appreciate a steady stream of lands. However, that's about all he does for them. Based on this, I think Wrenn will see play alongside Loam as a makeshift copy of the sorcery, but without Loam he's not really useful.
If the results from the MTGO release of Modern Horizons are any indication, Modern is due for a significant shakeup. However, it's important to remember that it's very early, and format inertia takes time to overcome. So far, I've found plenty of potential staples, though the format isn't quite right for them yet. I've also found that the Loam engine is viable and potentially quite powerful. The question is whether that power is enough given that the shells aren't obviously well-suited for Modern.