Very notably, the best rock deck in the format pre-Guilds is Black/Red "Rakdos Vehicles" while the best control deck in the format pre-guilds is some variant on Blue/White "Teferi Control." Neither Rakdos nor Azor get support in Guilds. this means that over and above both decks losing some sweet cards in the rotation, their mana bases just aren't going to be acceptable when the cycling lands go away and that's essentially the end of the decks. Here's a good article on why White/Blue decks are hurting so bad in the mana department.
So basically there are by mana-base fifteen different possible decks. That doesn't mean that there are only fifteen decks, just as you could play Rakdos Rock, Rakdos Aggro, and Rakdos Control in the previosu set, there will probably be Midrange and Control builds of several color combinations and as more cards are revealed we will get an idea of what kind of slick combo decks are on the table now that Paradox Storm and God Pharoah's Gift are rotating out.
Mono Colored Decks
It's rare indeed to see a mana base that doesn't support single colored decks. I'm not one hundred percent sure how that would work.
- Mono Blue Aside from a few weird fringe decks like Blue Flyers and Slitherthrone, Mono-Blue has been strongly associated with Paradox Storm. Kaladesh is rotating out, so this deck is most likely dead. You still have Sai, and there are more Guilds cards to reveal and Izzet is in the mix, but basically the Paradoxical Outcome is gone, all the Improvise cards are gone, including Statuary, and the Resevoire is gone. There's no deck. Unlikely that Mono-Blue is going to be much more than a fringe aggro flyers deck.
- Mono-White Monument is gone. Mentor of the Meek and the various Leonids are still on the menu, but there's no particular reason to play Mono-White any more. At the very least splash some Green.
- Mono-Green There is a deck called "Mono-Green Stompy" that is usually mostly Mono-Green with a splash of Blue or Black. Splashing Blue is significantly harder now, and one of the main draws of Black mana was actually Kaladesh artifacts which are out of the format. Which means that the actually Mono-Green version of Mono-Green (the one that puts Blanchwood Armor on Vine Mare and Carnage Tyrant) is that much more appealing. But a lot of decks people call Mono-Green will actually be Abzan moving forward.
- Mono-Black There are two Mono-Black decks that are tier 2 at the moment. They win a decent number of games but aren't big parts of the meta for various reasons. Mono-Black Aggro is a low to the ground aggro deck that is made with or without a Zombie synergy plan; and Mono-Black Control is a pile of disruption on top of some ridiculous big-mana haymakers that end the game. Mono-Black loses the Aetherborn vampires, which hurts the early game of Control and basically kills the non-Zombies version of Aggro. Control is further hurt by the fact that they lose some of their best win conditions in Torment of Hailfire and Cruel Reality. Obviously they still have great disruption and access to stupid huge quantities of mana in the late game, and they could very plausibly get a new win condition - but it's equally probable that they don't or that you'll be just better off being Blue/Black control. The big question mark hangs over Mono-Black Zombies, because they keep Stitcher Supplier, Diregraf Ghoul, Graveyard Marshal, Death Baron, and Liliana Untouched. That's most of a Zombies deck right there. But the deck loses Lord of the Acursed and Liliana's Mastery and now only has one Lord effect unless there's new Zombie leadership available in Guilds. So probably the various flavors of Mono-Black are just dead for the moment, thought we may see them rise again in a set or two.
- Mono-Red The Mono-Red Aggro deck of the moment is often called "The Flame of Keld" and it is usually a good sign for a deck if the card it is named after survives rotation. The Flame of Keld is still Standard Legal, and so is Wizard's Lightning, Goblin Chainwhirler, Viashino Pyromancer, Ghitu Lavarunner, Lightning Strike, and Shock. That's most of the deck. But there are some nice 2-cost cards that are lost (Kari Zev, Abrade, and Earthshaker Kenrha all go bye bye), but the most critical issue is that the Flame loses some critical 1-drops. Bomat Courier is an insane card that sees play in legacy because it refills your hand on turn 5, and Soul Scar Mage is a good combo with burn and also is critically a 1-cost Wizard for purposes of Wizard's Lightning. The 1-cost Goblins currently available are a substantial downgrade, though it's highly likely there will be some kind of 1 cost red creature to consider from Guilds considering that Boros is one of the Guilds. This deck will definitely stay as one of the named decks, but whether it stays Tier One or not depends on what cheap options are available.
Guild Decks
- Boros (R/W) The Boros mechanic is "mentor." If you attack with at least two creatures, you can put a +1/+1 counter on a creature with a lower power than a creature mentor for each creature with mentor. The typical case will be attacking with Goblin Warboss (2/2 mentor) with the haste token he makes each turn (1/1) and putting a +1/+1 counter on that token creature. But not very many Boros creatures have been revealed, and it's highly likely that there will be a few more killer apps. Obviously, putting counters on things that have lifelink and doublestrike is reasonably exciting and historically Red/White decks have had access to that sort of thing. It also plays well with auras and equipment since if you make a mentor a 3/3 it can put a counter on something that was already a 2/2.
It's very possible that a Boros deck won't come together on the grounds that you'd just rather be mono-red and beat face. But the mana's pretty good and Legion's Landing plays very well with the go-wide aggro plan and the Mentor mechanic. I'd rather put mentor counters on Vampire Soldier lifelink soldier tokens than Goblin Soldier do-nothing tokens. - Dimir (U/B) The Dimir keyword is Surveil, which is fucking Gravescry. You look at X cards on the top of your deck and put as many as you want on top of your deck in any order and the rest go in your graveyard. This works really well with cards that do things in the graveyard and Black randomly has Golgari cards that count the number of creatures in the yard for doing stuff and Blue randomly has Izzet cards that can be flashbacked by discarding a card. So Black and Blue are both very interested in dumping cards in the graveyard and of course Scry is very powerful and useful even without that. Obviously there is a lot of synergy there. And they get a new strictly better Dissolve, which is usually a good sign for a Blue/X control deck. What we don't have is any indication as to whether Dimir Control or Dimir Midrange actually going to be a viable deck. Scarab God and Torrential Gearhulk are both rotating, so the color combination's historical "top end" is gone and we haven't seen a decent replacement. Further, Glint Sleave Siphoner and Champion of Wits are both rotating as well, so the deck's early card draw plays are off the table as well. There's still Hostage Taker and Chupacabra, and the counterspell suite hasn't gotten any worse, so there's probably a deck there - but I'm not sure what it looks like. It might even be time for Pirate Tribal Aggro-Control.
- Izzet (R/U) The new Izzet mechanic is Jump Start. If a Jump Start Instant or Sorcery is in your graveyard, you can exile it, discard a card from your hand, and pay its normal mana cost to cast it a second time. Unlike Flashback it doesn't give you card advantage because it costs you a card to reuse it. But also unlike Flashback, the second mana cost isn't increased. So if a Flashback card is good, you can essentially have 8 copies of it in your deck and you get to decide what to cut for the extra copies in the middle of a game. So far, the only Jump Start card that's even "not bad" is Quasiduplicate - a three mana clone effect that seems "basically fine" as a Jump Start spell. Where you'd think Jump Start would be good is on Burn, since you can discard Lands for the extra castings - but honestly the burn spells revealed so far are so cautiously designed that they seem pretty bad. 2 damage to any target at Sorcery speed for 1RR. That's just sad. Izzet is already standing on a mostly workable Wizard Tribal Spells-Matter tempo deck. And people are basically always trying to get Blue/Red Control to work.
- Golgari (B/G) The Golgari mechanic is "Undergrowth" which doesn't actually do anything. Yes, really. When a card says "Undergrowth" it asks you for a number and that number is the number of creature cards in your graveyard. What the card actually does with the number could be anything. Sometimes it's real good, sometimes it's basically meaningless. It's highly card dependent and we haven't seen most of the cards. Now Green/Black has lots of efficient ways to fill the yard. There are zombies that self-mill, there are the Explore cards from Ixalan, and now there are whatever Black Surveil cards show up. So there's certainly the enablers for a Golgari Graveyard deck. But we don't have the payoffs. If we get a good sacrifice outlet, it might just be that we ignore the Undergrowth cards for the most part and just use Journey to Eternity to continually sacrifice and reanimate Jadelight Ranger, Reclamation Sage, Chupacabra, and finally Pelakka Wurm. If there's an actual win condition hiding in the Undergrowth, then maybe we just mill ourselves to victory. Regardless, it seems easy to imagine such a deck being somewhere on the spectrum from Synergy-Midrange to Combo-Control. If the Undergrowth payoffs aren't good and there isn't a sacrifice outlet at least as good as Yahenni, I think the guild probably DOA.
- Selesnya (W/G) By far the hardest guild to spell and to say, I feel confident in saying that from a branding standpoint it was fundamentally wrong to name the White/Green Guild Selesnya. In any case, the faction's new mechanic is a returning old mechanic: Convoke. Convoke spells are generally overcosted for what they do, but you are allowed to tap any of your creatures like they were mana dorks to pay for them. If that doesn't sound like a winning combination, I think the word "generally" is doing a lot of work there. Some historical Convoke spells actually aren't overcosted to begin with and then Convoke is just a bonus. Also, since technically it's the Convoke spell tapping the creatures it ignores summoning sickness so it's good for double spelling as you can play a creature and then tap it for convoke. The big reveal is that the Cast Out replacement has Convoke instead of cycling and Flash. That makes it much worse for Control decks and much better for Aggro and Midrange decks. In any case, the theme for Green/White is "go wide" and there are a number of cards like Legion's Landing and Emmara that can let you go very wide, and cards like Shanna that pay you off for going wide. It's a deck that hasn't really worked very well in the pre-Guilds standard, but hopefully the Chainwhirler decks that make go-wide strategies cry are becoming less common.
Three Color Decks
- Abzan (W/B/G) Abzan is a majority Green deck. And as such, it is the only 3 color deck that can reliably cast a turn 1 Llanowar Elf. That in turn means that Abzan is likely to be the go-to color combination of what is currently known as "Mono-Green Stompy." So basically we expect it to be heavy green with mana dorks and beat-down creatures and using it's white and black splash for disruption and countermeasures for control. This is a solid candidate for Tier 1 deck.
- Naya (R/G/W) Naya is a majority White deck. So while it's broadly speaking the colors of Dinosaurs, and there might be a Dinos deck in there, it's mostly just a White go-wide deck that splashes Green and Red for mentor and token generation. The big question I think is how much you're supposed to rely on City's Blessing mechanics. Some of the top slots for turn 1 plays are Skymarcher Aspirant and Legion's Landing, and Mentor is a pretty good combo with Snubhorn Sentry. The big question is whether Naya is better than Boros or Selesnya, because it's very possible that one of those three builds is just better than the other ones and that all White/X go-wide decks converge to one color combination.
- Sultai (G/U/B) Sultai is majority Black and runs Golgari and Dimir cards. It's set up to be graveyard.deck, but like its components it's not exactly clear what the payoff is. You can play a turn 1 Stitcher's Assistant, which is a great start for a deck that wants to mill itself to victory. But... then what? You got some decent means to buy things out of your graveyard (Isareth, Muldrotha, Journey to Eternity), and some decent value creatures to buy out of the graveyard (Hostage Taker, Reclamation Sage, Chupacabra), so maybe you just grind it out as a Midrange deck with a lot of self mill. But if there's a killer app for either sacrificing creatures for value loops or doing something ridiculously broken with a big graveyard then you'll do that.
- Grixis (B/R/U) Made out of Izzet and Dimir, Grixis actually has a clear top end. You make Nicol Bolas, the Ravager, and then you either smash face with a four mana flyer backed up with removal and counterspells or you grind things out until you can flip Nicol Bolas and crush your opponent with the value train. It's base blue and there aren't really any blue cards you want to cast on turn 1, but the mana is good to start casting Search For Azcanta or counterspells on turn 2. You have Red and Black removal cards for things that slip through your web of counters.
- Jeskai (U/W/R) Honestly, I think this is where the wheels fall off. Any Blue/White deck is going to try to make itself be about Teferi, because Teferi is ridiculously powerful. But Jeskai is a Red deck that splashes Blue and White. And I'm not sure that there exists a Red deck that wants to tap out for a five mana Planeswalker that gives you bonus mana you can only spend on your opponent's turn. I think Jeskai is going to be pretty bad, because in most cases it's going to be a Boros deck that splashes blue for one broken planeswalker that doesn't synergize well with the rest of the deck.
