Just as Boros and Selesnya get to share the white cards in the set the black cards get split between the two remaining guilds. As black contains most of the removal spells in the set there are a lot of cards these two guilds fight over. Luckily both guilds try to win in different ways and so there are differences in the cards they look for.
Of all the guilds the Golgari seem to have it roughest in terms of the cards they actually want for their deck. Like Selesnya, the Golgari share both of their colours with another guild, which means a lot of their main cards are sought after by other drafters at the table. While this is also true for the Selesnya guild, there isn't the same depth amongst the Golgari commons that the Selesnya drafters are used to.
First off, any deck that is Golgari instead of Selesnya has to use the black commons instead of the white ones. While the black spells are definitely better the creatures are considerably worse. There are a lot of solid common creatures that Selesnya decks have access to: Benevolent Ancestor, Conclave Equenaut, Nightguard Patrol, Screeching Griffin and Veteran Armorer are all solid additions to any deck.
In black the best attacking creature is Dimir House Guard. After that things get shaky right away. Mortipede can be good, but can also be too fragile when you're actually looking for a creature that will deal damage to an opponent. Stinkweed Imp can hold off all manner of attackers but isn't particularly adept at dealing damage itself. Sewerdreg is another card that's great against some players on the table, but a lot worse than comparable creatures against players without a Swamp in their deck.
The result of this is that Golgari decks often have to rely heavily on green and on their guild cards for the creature count. This is all well and good but the best green creatures are also getting snagged by the Selesnya players. The Golgari guild features two excellent common creatures in Golgari Rotwurm and Shambling Shell but also one not-so-great card in Woodwraith Strangler. The Strangler will sometimes have to be included in a deck if you're short on playable guys but you'd usually be much better off splashing for something else entirely. I've never had the Strangler be good in a game yet. The Rotwurm and Shambling Shell are both very efficient creatures though, and are exactly the sort of creature you want in a Golgari deck.
Due to the fact that the Golgari decks often feel like they're drafting from a smaller pool of playable cards, this is one archetype I tend to draft only if I think I am being passed it. If you have another Golgari drafter next to you then you'll both be in a lot of trouble. It's difficult sometimes to work out when this is happening but being passed some of the best Golgari commons like the Rotwurm, Shambling Shell and cards like Last Gasp are pretty good indicators that you've been given the green light.
When it comes to drafting Golgari decks I think you have to do so in a very different way than how you would draft Selesnya. That might sound obvious but it has implications on how you rank the green commons shared between those decks.
In my experiences with Selesnya, that deck is best drafted when focused heavily around the Convoke mechanic. It has numerous commons that reward that focus and the result of that is cards like Scatter the Seeds, Siege Wurm and even Fists of Ironwood become very high picks for that deck. Golgari doesn't have the cards to support the Convoke mechanic, even though that mechanic is present on some of its green commons. The best Golgari decks I've drafted have simply focused on drafting efficient creatures, and having a good mana curve. They then back these up with the cheap black removal spells. For this reason my top common picks for the Golgari decks are very different.
I also really like Mossdog in Golgari decks as it actually fits the mana curve very well at a point where the only other card that really fits is Dimir House Guard (Mortipede has the same cost but you want cards that are difficult to block effectively early in the game). The addition of the Dredge mechanic on Mossdog is surprisingly relevant but I'll discuss that more in a while.
I'd probably take Civic Wayfinder and Elves of Deep Shadow over Scatter the Seeds, but below Siege Wurm. Even at five or six mana Siege Wurm is pretty efficient and is still playable but Scatter the Seeds isn't so good in Golgari decks as it only gives you three points of power and toughness for five mana. You also don't have Seeds of Strength available to boost up those Saprolings. That's not to say you wouldn't draft Scatter, just nowhere near as highly as you would in Selesnya decks. Scatter can sometimes be very effective with a Rotwurm in play but you'd still rather have another efficient creature if you had the choice.
The Dredge mechanic has been fairly useful for me lately, as it's a fine way of ensuring you don't run out of gas. Shambling Shell is the obvious standout card here as it's efficient in the early game and still useful late game too. There are several games I've played where the best option was simply to recur the Shell every turn to add counters to a Dimir House Guard that was getting through unblocked. Having that option is very nice in some situations.
There are also games where your Shambling Shell and Mossdog get traded off early and you just bring them back once or twice so you're able to continue applying pressure to your opponent. Against some decks this won't always happen of course; when playing against Selesnya they might be nullifying them by blocking with Saprolings or a Dimir deck might have a Drift of Phantasms holding them off. However sometimes you will be in a game where creatures are getting traded off and when that happens Dredge really becomes a great ability.
The other Dredge common that has useful applications is Stinkweed Imp. Golgari decks are often vulnerable to flyers and the Imp will often threaten to take out several opposing flyers over the course of a game. There are ways to deal with it of course – Faith's Fetters, Benevolent Ancestor, giving their flyer first-strike, etc – but your opponent isn't always going to have the answer they need.
Here's a solid 3-0 Golgari deck:
As you can see, there's no real funny business here. Just a bunch of solid creatures, a good mana curve and some cheap removal spells. Pretty much the best draw you can get with this deck is turn one Elf, turn two Shambling Shell, turn three Mossdog, turn four Rotwurm. That's your ideal opening and those are the commons that get valued highly because of that. The Golgari decks that have been successful for me don't spend time messing around with Saprolings or trying to splash a third colour, they just play efficient creatures that hit the opponent hard and fast. You've then got the Dimir House Guard and Rotwurms to finish any opponent off who successfully stabilises the ground.
Of the four main archetypes it is Dimir that has given me the most trouble in coming up with the ‘best deck' for its guild. Half of the Dimir commons are cards like Dimir House Guard, Roofstalker Wight and Snapping Drake. The other half are Lurking Informants, Vedalken Entrancers and Induce Paranoias. The two groups just do not go together very well.
It's probably a little easier to draft the evasive Dimir deck than the milling Dimir deck. There are a reasonable number of common flyers that do an acceptable job in the evasion department. Roofstalker Wight is cheap and can usually get a hit or two in early on as the other decks don't want to trade their Selesnya Evangel or Warsong Trumpeter for it. Later on he flies over fairly regularly and two damage a turn is fine. Dimir Infiltrator is another acceptable two-drop as it can stall some early damage while you set up and then aid in the offence later if required. Moving up the curve both Snapping Drake and Tattered Drake are quite playable. While there isn't a standard 3/3 Flyer for five mana, Snapping Drake fulfils that roll although it does unfortunately only trade with Skyknight Legionnaires and Screeching Griffins due to the lacking point of toughness. Tattered Drake is surprisingly useful even though you're paying a little over the odds for it. Paying an extra two mana for “: Regenerate” (which is what you're paying when you compare it to Wind Drake) is a little excessive but the creature is able to both stall attackers and go on the attack itself when required. It'd be an excellent common at four mana and you don't really mind paying five at the end of the day.
Vedalken Dismisser is a card that looks very expensive but that actually turns out to be quite fair. Time Ebb is three mana and a Gray Ogre costs three so getting both in one card for six is actually respectable. The Dismisser can have a nice effect on tempo as it's able to remove their best guy for a full turn, cost them a draw step, and perhaps trade with something else. He also combines very well with Peel from Reality and if you ever pull that off you'll create a lot of extra time for your flyers to steal the game.
You really do have to focus on drafting a specific style of deck when drafting Dimir though. Those Vedalken Entrancers have no place in the deck if you don't have the other cards to back them up. You should definitely be taking 'filler' cards like Surveilling Sprite and Compulsive Research over them in a draft if you want to have enough playable cards to fill out the deck otherwise you just end up with overcosted counterspells and 1/4 creatures with no real abilities.
Here's an example of a typical evasive Dimir deck:
This style of deck can be tricky to draft as it's very much a tempo deck. It's creatures aren't usually going to be better than your opponents so you need to win the game before this actually matters. Tempo cards like Vedalken Dismisser and Remand are important, as is having access to the cheap spells like Clinging Darkness and Peel from Reality. Twisted Justice might be weak in the above deck, but it was the best alternative available in this particular deck.
As the deck relies so heavily on the Entrancer you should only really consider drafting it when you're able to get one early in a draft. They are only useful in this particular archetype and they do frequently go around the table late, but if there's another Dimir drafter or they simply don't get opened there's no guarantee you'll pick one up late in a draft.
The second best blue common for this archetype is almost certainly Tidewater Minion as you can use this to untap your milling device and get double use from it. The Minion also functions as a very large wall that only the biggest of creatures can get past. You don't need too many turns of Entrancer + Minion activations to get rid of a 40 card deck. In this archetype both of these cards should be taken over every other common, with the possible except of Last Gasp.
Lurking Informant is another fine addition to this archetype. It helps out a lot in the mid-game as you can choose to leave lands on top of an opponent's deck which will make it difficult for them to draw enough threats to Overwhelm you before your Entrancers can dispose of the opposing library. The Informant also excels against any opponent who is having mana problems. I've won several games on the strength of an Informant disrupting the draws of an opponent who is obviously light on lands or missing a colour. Giving them a stream of unplayable cards while you continue to develop your board position is nice and will sometimes be relevant.
In addition to the cards that actually win the game you also want other cards that help stall the opponent's attack. Dimir Infiltrator and Drift of Phantasms are both good at this and Tattered Drake also fulfils a good role as a defensive regenerator.
You'll probably want a decent amount of removal if you can get it and you don't mind if it's particularly slow. I'd happily play Stasis Cell in this deck for example and the Stinkweed Imps and Clinging Darknesses are also high picks for obvious reasons. They're all useful and they all help give you time.
The deck should be filled out with card drawing and anything else that helps with the milling theme. Belltower Sphinx and Psychic Drain are both excellent and you don't mind Induce Paranoia too much either. Dimir Guildmage is another great card and Compulsive Research fulfils a nice card drawing role too.
The Transmute mechanic actually has a bit more play here as you can Transmute Dimir House Guards into Vedalken Entrancers, which is often useful in this archetype. You can also Transmute Drift of Phantasms and Dimir Infiltrator into various useful cards depending on the situation you're in. While this is slow, this deck aims to be able to stall and Transmute definitely has more play in this archetype than it does in the evasive beatdown deck.
Your decent Dimir milling decks should end up looking something like this:
That concludes the initial look at the four guilds and the sorts of decks you might expect to see in the first few weeks of drafting with Ravnica. I'm sure new deck types will emerge over time but this is what we can expect for now.
You might also see focused multi-colour green decks drafted and right now I'm still not sure if any non-Guild colour combinations might still be playable. A blue-white deck full of ground stall and flyers has always been popular in limited for example and that still might actually be draftable here. You could well see a blue-white deck splashing only for Sunhome Enforcer, Lightning Helix and Galvanic Arc for example. These are the sorts of things I plan on exploring over the coming weeks.