I think almost everyone can agree that Modern was in a great place before the unbanning of Jace, the Mind Sculptor and Bloodbraid Elf. It might still ultimately be in a great place, but the Magic Online Championship was a little troubling. Seven of twenty-three players played Jund, meaning the deck represented 30% of the field, or more than three times as much as the most played deck at the last Pro Tour. Now, a small field like the Magic Online Championship is much more likely to skew toward one deck since a few players have a large impact on the percentage, and the players are all the same type of highly competitive player, whereas a Grand Prix will be more likely to bring in players with different goals or approaches to Magic tournaments. That said, it would be pretty bad if Jund continued to occupy anywhere near 30% of the metagame.
It's not that Jund is unbeatable or that Bloodbraid Elf is broken, the fear of unbanning Bloodbraid Elf is that it would collapse several different archetypes (Jund Death's Shadow, Abzan, and any other G/B/x roughly midrange deck) into one single archetype with a very close consensus build. When this happens, it shrinks the format around it, as it becomes a sole target, so people move to decks like Burn, G/W Hexproof, and Tron that are expected to do well against Jund, and linear decks like Humans and Affinity get pushed out of the format.
As someone who would love to see Modern stay fun and healthy, I'd rather encourage people to find creative new ways to beat Jund than just recommend playing one of those decks to try to keep it in check, since that mentality can still collapse the metagame. Of course, as competitive players looking for the best possible edge in your next event, you'd probably do well to ignore me. Modern may be vast and surprisingly unexplored, but a vast majority of new experiments will fail.
For those who are still with me and would like to try to find a new answer to Jund, I'd like to show you what I've been thinking about this morning.
Breaking Hidden Stockpile in Modern has been a goal I've had on the backburner for a while. It's such a powerful card, and revolt is so easy to trigger in Modern that I really feel like it should be great in the right shell. Also, as Jund trims its answers to enchantments, as we saw in Steve Rubin's build in the Magic Online Championship , it starts to sound to me like a card that might be pretty good against Jund.
Previously, I'd primarily tried using it with fetchlands to trigger revolt, but this morning, I thought about Mishra's Bauble and Chromatic Star. Once I had those in my deck, Mox Opal started to sound pretty appealing, but I'd need to find a way to get more artifacts in my deck. Terrarion works pretty well. My next step was an odd leap--once I had Terrarion and Chromatic Star, what about Crack the Earth? That's a good way to trigger revolt.
Crack the Earth is pretty good with Chromatic Star, but it's even better with Ichor Wellspring, but you can do even better than that--Hatching Plans. Hatching Plans is a bit of a pet card ever since a weird old Standard deck I played that used it with Perilous Research and Claws of Gix. The thing about Hatching Plans is that you can't just play it with four Crack the Earth and hope they line up, you need other ways to sacrifice it. Perilous Research sounded fine, and a quick search for "sacrifice a permanent" lead me to Angelic Purge, not the strongest card in a vacuum, but maybe exactly what I was looking for.
So now I've filled out most of a deck, but none of my cards really do anything. If this mess is going to have any chance, it's going to need some more interaction and some way to actually kill my opponent. Here's where that led:
There's a lot of weird stuff going on here. Once I'm at the point where I'm trying to play Hidden Stockpile, Crack the Earth, and some blue cards, I'm basically committed to a five-color manabase, rather than a fetch/shock manabase. Given that I already wanted Chromatic Star, Terrarion, and Mox Opal, my mana's going to be pretty good, but given that I'm actually trying to avoid using Terrarion and Chromatic Star for mana whenever possible, it's not quite as easy as it sounds. However, once I have eight zero mana artifacts and eight one mana artifacts, it's easy to include Glimmervoid and Spire of Industry, and now I have a floor of twenty sources of each color, so I can really do whatever I want. My total artifact count for Mox Opal is still a little low, and I want it to turn on as soon as possible, so I'm pretty sure I need four Darksteel Citadel. That's twelve lands I'm sure I want to play. That leaves probably four or five lands to work with.
Those can really be basically anything. I wanted a couple basics so that I could find them when my opponent made me search my deck with Field of Ruin, Ghost Quarter, or Path to Exile, and I figured Hidden Stockpile is my hardest card to cast, so I'd use the basics that can help cast it.
I considered rounding it out with Aether Hub, but I don't expect that I'll need the help casting my spells, and decided I'd be better served by getting some utility lands in the deck. I opted for Ghost Quarter over Field of Ruin because I don't really care about finding a basic if I'm activating my land in the midgame because this is the kind of deck that tends to flood out despite the low land count because it's mostly just card draw, and I'd like to be able to activate it whenever I need to. Darkslick Shores is a bit of a hedge that may be inappropriate. It could easily be another Ghost Quarter, an Inventors' Fair, or whatever else; maybe it shouldn't even be a land.
I considered playing a couple fetchlands and a couple shocklands to trigger revolt and help boost Tarmogoyf early, but playing shocklands felt like a pretty big drawback given that I'd only have room for 2-3 fetches total.
Once I figured out the core and had only a few slots left to kill my opponent, I needed to figure out the most efficient way to do that, and I settled on Tarmogoyf. I figure I can generally count on my opponent to put lands in the graveyard, and I'll be putting artifacts in the graveyard early almost every game, so I think Tarmogoyf will usually be around a 4/5 pretty early. The efficiency is important because I'm wasting so much mana drawing cards, so I need my finisher to be cheap and high impact. The problem with Tarmogoyf is that it's relatively easy for the opponent to answer with a single card, but I'm generally happy to trade one for one, since I draw so many cards. With Tarmogoyf, at least I won't be down much mana. Besides, if I need resilience rather than speed, I still have Hidden Stockpile.
For interaction, I already had Crack the Earth and Angelic Purge. Crack the Earth doesn't really count, since it never really answers anything; it just kind of generically slows the opponent down while helping my deck function. Just as with threats, my priority was to find cheap interaction to help make up for the tempo loss of spending a lot of mana cycling through and drawing cards. I went with Fatal Push over Path to Exile because Path to Exile really doesn't make sense when you're playing Crack the Earth and I already have Angelic Purge to answer expensive creatures. Besides, obviously my deck is already built to trigger revolt whenever I want, so Fatal Push will be at its best.
It's nice that Angelic Purge gives me maindeck answers to artifacts and enchantments, but in Modern you also need to be able to interact with your opponent's spells. Thoughtseize is a great catch all, but not what I'm looking for here because I always want to be able to spend my first turn playing Chromatic Star or Terrarion. What I'm looking for is a tempo positive maindeckable card that stops spell decks from killing me, since my clock isn't terribly fast. I settled on Metallic Rebuke, since I think I'll often be able to cast it for one mana if I'm a little careful about stuff like when I cash in my Mishra's Baubles, which I want to be anyway as a consideration for Hidden Stockpile and Mox Opal.
Snapcaster Mage and Liliana of the Veil round out the deck - once you've cast Crack the Earth, the best thing you can do is often casting more Crack the Earths, but I couldn't go overboard on Snapcaster Mage because I don't have that many total spells in my deck for it. Liliana of the Veil is a generically good card that puts another card type in my deck for Tarmogoyf, plays well in small games, which means it complements Crack the Earth well, and it attacks from a different angle, which is nice. That said, it's possible that I'd rather just have another Metallic Rebuke.
The last weird hedge is the 2-2 split between Hatching Plans and Ichor Wellspring (as well as the 3-1 split between Angelic Purge and Perilous Research). I'm not playing any cards that sacrifice artifacts that can't also sacrifice enchantments, and the purpose of both cards is to sacrifice them. So on its face, Hatching Plans is the stronger card, but Ichor Wellspring draws one card immediately and one later, which can be better than three later depending on how much later it comes. It also contributes to metalcraft and improvise (though it's also a worse type for Tarmogoyf). Ultimately, I'm not sure what the perfect mix is, but this felt like a reasonable starting point.
As for Perilous Research and Angelic Purge, I was originally on a 2-2 split, since Perilous Research seems like the stronger card, but after realizing how much air is in the deck (the number of cards that just replace themselves rather than impacting the battlefield) I realized that I'd rather have interaction in that role. There's a good chance it should just be four Angelic Purge, but that seems like a ton of three mana sorcery speed removal spells, and Snapcaster Mage prefers the variety and the instant is nice with Metallic Rebuke.
The sideboard is a pretty wide open question when colored mana isn't a concern, and the only real driving principle of the deck is value; at the same time, the deck is full of cards that kind of rely on each other to function properly.
Nihil Spellbomb is an easy choice - it's on plan enough that it could easily be included in the maindeck and good at what it does. Additional Fatal Pushes and Metallic Rebukes felt similar, although it's possible that Negate would be a better sideboard card than Metallic Rebuke.
Pithing Needle is a generically good sideboard card that's a great fit in an artifacts-matter deck like this, and it could easily be right to play more of them. Engineered Explosives is fantastic here, since I have five colors of mana, and sometimes it gives me another way to profitably destroy my own Ichor Wellspring or Hatching Plans.
Ultimately, I think I'm a little heavy on cards that just say, "destroy a thing" - I might need more countermagic, but what I really feel like I'm missing is a better backup plan for when Tarmogoyf isn't a good finisher, like when my opponent has Rest in Peace. I'm not sure what's best - it could be more planeswalkers, any combination of Liliana of the Veil; Liliana, the Last Hope; Tezzeret, Agent of Bolas; or Jace, the Mind Sculptor could make sense--or it could be some other creature, though I'm not sure what the best combination of efficient, resilient, and "doesn't need the graveyard" is. Maybe Hazoret? I'm not sure if I draw too many cards for that, but it could probably work. The Scarab God? Kind of expensive and really prefers the graveyard. Olivia Voldaren? Powerful in some matchups, but not especially resilient. Thought-Knot Seer? Often remarkably bad at actually winning on its own.
Another consideration for this deck was Smallpox, especially if I wanted to use the flex land slots on a few Flagstones of Trokair and maybe a Godless Shrine. I like that it combines generic pressure on their resources with Crack the Earth and Liliana of the Veil, but I don't like that it ignores all the cards I'm actually trying to sacrifice. I could also see it as a sideboard option for matchups where making my opponent sacrifice a creature is particularly good and/or when I'm on the draw.
So how competitive is this deck? I'm not really sure. It's a weird house of cards, but it has some interesting things going on and some cool clusters that could be slotted into other decks or paired with other ideas, so it feels like the kind of thing that's useful to explore as a brewer, but I'll fully admit that my goal here was more to walk through how I approach trying to find something new in Modern than to recommend a hot new deck for SCG Dallas.