Having seen the full spoiler for March of the Machine: Aftermath, I'm thoroughly underwhelmed. As I mentioned last week, this set feels more like a carved-out piece of the main set than anything unique. Specifically, a piece that was carved out as Commander fodder, as most of the cards seem specifically designed to be used as commanders.
That said, there are a few cards that could make normal constructed formats. Assuming there's a need to fill their very specific niches. Today, we'll explore the most exciting standouts for Constructed play.
There is no shortage of three mana white hatebears with niche effects. The one that's seen the most play is Archon of Emeria, as Rule of Law stapled to Kismet is quite potent. The new addition, Metropolis Reformer is unique but isn't going to beat Archon for any slot.
Adding vigilance and a relevant creature type is a solid start but aren't relevant to playability. What matters is the actual hate effect, and Reformer's is too niche for widespread play. While giving players hexproof is sometimes relevant, the previous white creatures that did so (True Believer, Aegis of the Gods, and Keen-Eared Sentry) have never seen much play.
The problem is that all of these creatures are extremely fragile. Leyline of Sanctity still sees play because enchantments are hard to kill. If an opponent really needs to target you, they'll have a way to kill the creature. Also, most of the time the only effects targeting players are discard spells, and other than Leyline, none of these cards are fast enough to protect against them.
The Natural Home
Pioneer Angels could fit Reformer in with no issue whatsoever. I just have no idea why it would bother. Mono-Red is not a difficult matchup, and that deck doesn't go face with its burn much anyway. The lifegain is nice there, but not crippling. It might see play to slam the door shut, but there's no pressing need there, and Angels has other problems to sideboard against.
The other combo decks have ways to remove Reformer and/or win conditions that don't target. Mono-Green Devotion can simply wish for Skysovereign, Consul Flagship or Cityscape Leveler. Lotus Field has Otawara, Soaring City and Approach of the Second Sun. Against everything else, Reformer is an okay threat, but just doesn't stand out.
The Special Niche
I don't think Reformer will see Pioneer play. If it does see play outside of Standard, I suspect it will be in Modern. There, Reformer is easily the best anti-Burn card printed in years. The only card that's more devastating is Collective Brutality, at least among maindeckable cards.
Reformer is immune to Searing Blaze, which is a great start. The hexproof means there's no getting around it: Burn players will have to remove it to make their deck work again. Removing it with damage gains life, meaning that Reformer represents a net of -2 cards to the opponent. The first card is lost killing Reformer, and the second comes from the three life gained, which is an entire spell's worth of life. All without having to discard your own cards.
There's really no need to be this worried about Burn for most decks. Burn isn't that big a piece of the metagame, and there are lots of ways to answer it already. However, if that ever changes, here's a very strong answer.
Jirina, Dauntless General
Every time a new, even marginally useful human is printed, players always act like it's the thing that will return Humans to the top of the metagame. Never mind how many times it's been said already that this is the one! Please also ignore that Humans returned to the metagame recently by rediscovering the 18-year-old Shining Shoal. No, it's new cards that will revive the deck. Is my eye rolling coming through?
Aftermath is no exception, and there are a number of potential Humans cards within. The most commonly cited card is Coppercoast Vanguard. 2/2 for two is a standard rate, and increasing Humans' power and giving them ward isn't bad. However, the fact that none of that applies to itself is fatal, literally. Opponents will just kill it first or sweep the board rather than worry about the ward triggers.
Jirina, Dauntless General is a slightly different matter. Her sacrifice ability has been touted as a way for Humans to finally beat Akroma, Angel of Fury. Again, please forget about Shoal. True, Jirina does also protect against Supreme Verdict, but UW Control doesn't always run that card anymore. These types of effects work great when they're surprises, but are mediocre otherwise.
The Natural Home
Obviously, Humans could play Jirina. However, that would require Humans to regress to an earlier era of the deck. The current version sacrifices Aether Vial in order to gain Shoal, and to an extent Emeria's Call // Emeria, Shattered Skyclave. This has weakened Humans against some decks but has proven worthwhile enough against the top decks put to get Humans back in the game.
Selfless Spirit saw a lot of play, but had the benefit of being played alongside not just Vial but Rattlechains and Collected Company. Thus it got to surprise counter Verdict very easily, while Jirina will have Vial at most. This severely limits the critical surprise factor with this effect. Otherwise, opponents will just kill Jirina end step, untap, and then sweep the board.
The Niche Application
That said, Jirina is phenomenal against Living End. The first ability is obviously good as graveyard hate, but the second ability is still relevant. While it doesn't protect against having your board wiped, it can still be sacrificed before Living End resolves, ensuring that you have a creature afterwards. While facing a board of huge monsters is bad, having to rebuild your own from nothing is worse, and Jirina fixes that problem.
If Living End becomes enough of a problem for Humans to want Jirina, she'll need to justify two significant changes to Humans. First, the mana base will need a rework. Shoal has moved Humans to mono-white, and Jirina requires black mana. That might be easy, but it might also require giving up something to maintain balance. The other issue is that Humans would need to readopt Vial.
In a hypothetical metagame where Living End needs such a specialized answer, that all might be worthwhile. The metagame would likely shift away from red removal toward counters, making Vial more useful. Blood Moon might be less of a concern as Living End always plays Foundation Breaker, sometimes even maindeck. Outside of that kind of shift, I'm skeptical of Jirina.
Wizards rarely makes tutors anymore, so anytime a cheap one is made it is immediately scrutinized. Which is unfortunate for Reckless Handling, as it is rather narrow. Finding only artifacts isn't bad, but remember that Whir of Invention isn't played anymore. Making matters worse, Handling is a riff on Gamble.
Gamble used to be a staple in Legacy Lands because Lands always needed Life from the Loam and didn't care if it was discarded. That time has passed, and now Gamble is only found in red combo decks that similarly don't care which zone the tutored card is in, but just that it's out of their library. It's reasonable to assume that Handling will only see play in a similar deck.
The Natural Home
The only deck (I can think of) that sees any play and fits all the criteria for playing Handling is Jeskai Urza. It already runs Goblin Engineer to find Sword of the Meek, so Handling provides some redundancy and a marginal upside. Emry, Lurker of the Loch also means tutoring for any other artifact isn't actually gambling, but rather a guarantee that the artifact will end up on the stack.
The Big Problem
That's all well and good, but why would Urza bother with Handling? Engineer already does everything they need, and if another tutoring effect was needed, Whir exists. The fact that I haven't seen Whir in any Urza deck is a pretty strong indication that it just isn't good enough anymore. If a tutor that puts the card directly into play isn't good enough (and often costs no mana), how can Handling be?
The Brewer Traps
Every new set release leads to a surge in brewing, which is no bad thing. However, there are always a few cards that are effectively traps. They look like strong cards to either build around or provide so much theoretical value that they can't resist putting it into every deck, regardless of their deck's actual need for the card or overall strategy. Aftermath has several cards that will certainly prove potent traps.
Paradoxical Outcome is a Vintage-defining card, and Filter Out has shades of its utility. While there's a case for using Filter as a way to clear boards of prison pieces, Modern and later formats have Hurkyl's Recall for that job, and that's one sided. Filter not targeting will be mostly, though not entirely, irrelevant, while costing one less mana is always relevant.
Therefore, it is extremely unlikely that Filter would be used for any reason except to fill Outcome's role. In Vintage, I could see it making the cut as additional Outcomes, though significantly worse. Given that Outcome doesn't see play in Modern or Legacy as is, there would need to be a new combo deck to make it work.
I've heard chatter that players are working on it with Urza, Lord High Artificer and zero-cost artifacts, but at that point, why not just play Outcome? Once Urza is out, mana is largely irrelevant, so the difference between three and four mana becomes trivial. What isn't is Outcome drawing cards, which Filter can't do. As Outcome also doesn't automatically destroy tokens, I think working on Filter is wasted effort.
This card is dripping with value potential. Instant-speed reanimation is extremely rare, and a spell that reanimates with upside is even rarer. Cosmic Rebirth may be limited to reanimating only three cost or less, but it can get any permanent. It can target higher costs too, though that's just being a bad Eternal Witness at that point. The life gain is gravy.
I've seen a lot of chatter about reanimating A-Teferi, Time Raveler in Modern in response to cascade triggers. Which I won't deny is really appealing. The issue is that such a situation isn't exactly optimal. Ignoring the possibility of Force of Negation, having Rebirth available to get around a failstate isn't the best use of a card. Furthermore, outside of that scenario, what exactly is Rebirth doing for any deck?
This is a card that almost any deck could play, but that won't do much for most of them. Yes, getting a land back to ramp is a thing, but three mana conditional ramp isn't really constructed-worthy. Pioneer, where I've seen this kind of talk the most, doesn't even have fetchlands to abuse. This is a card with too much value to ignore entirely, but unfortunately, it's useless value.
Aftermath doesn't have much for non-Commander players. What is available is quite conditional and/or deceptive. They have their uses and can be great, but only in exactly the right situation. While I expect to see some of these cards played against me, I doubt that they'll be setting any format on fire.