Legacy is not a pretty format right now. The best deck is a brutally effective, well-oiled machine that exploits any deckbuilding weaknesses across the table. It can get ahead of you on mana and play multiple meaningful spells a turn as soon as turn 2. It can accelerate into a planeswalker and warp the game around that one permanent. It can tear apart your hand with discard spells, quickly finishing you off with a hefty Tarmogoyf. It can disrupt your game plan with maindeck graveyard hate and versatile removal.
In short, the deck is prepared for almost everything.
What does the enemy look like?
No, wait. Sorry. This.
Wait, wait, wrong again. This one.
Sorry, this is a bit embarrassing. This is what I was looking for.
This is the spectrum of BUG decks. As you can imagine, there is no uniform way to beat all four of these builds. I've listed them here in order of how aggressive they can be. Just because someone plays an Underground Sea and then a Bayou doesn't mean that you can count on being alive come turn 5. Your opponent could very easily have a line of "Delver of Secrets, flip it revealing Daze, cast Tarmogoyf, and Daze your two-mana spell."
What unifies all of these decks?
4 Brainstorm: Beyond all of the draw-three-spells-shuffle-away-two-lands magic that it does, we're looking at a format that has significantly more discard than a few weeks ago. Holding your Brainstorms means being able to hide your critical spells (or lands) from opposing discard spells. When in doubt, wait.
4 Abrupt Decay: A Dreadbore / Krosan Grip split card. There are six real permanents that Abrupt Decay doesn't hit: Jace, Tombstalker, Creeping Tar Pit, Sneak Attack, Emrakul, and Batterskull. For everything else, there's Abrupt Decay.
4 Deathrite Shaman: One of the best cards in Legacy. It accelerates, it gains life, it demands an answer against control decks, it fights threshold cards, it shuts off graveyard decks, and it even attacks for one if it can't do the first five things. The turn where your deck starts casting multiple spells is an important one in Legacy. Deathrite Shaman jumps you a turn closer to that critical point.
A key thing to remember about Deathrite Shaman is the placement of the colon on its abilities. Activated abilities are templated "cost: effect," meaning that everything to the left of the colon happens as you start to activate Deathrite Shaman and takes place without you passing priority. Everything to the right of the colon is what you have to wait for. All three abilities are targeted, meaning that if the target isn't there when the ability tries to resolve, nothing happens.
Tapping your lands correctly extends to your Deathrite activations now, too. Think it through.
4 Tarmogoyf: The most efficient creature in the history of the format. A necessary stopper against aggressive decks and a necessary clock against combo decks, I wouldn't dare play a BUG deck without four.
The Discard Suite
Builds diverge wildly from here. People will play anywhere from four to ten discard effects, generally in the following hierarchy:
1. Hymn to Tourach. If the format is grindy and you want to turn games into cardboard-counting competitions, there's no cheaper way to get two for the price of one. If you're closing out games quickly, though, you may care more about stopping specific spells than getting a good bulk-order rate.
2. Liliana of the Veil. A removal spell with a ton of upside. A way to pressure combo decks. A way to fight an opposing active Jace. One of your only playable answers to the Show and Tell monstrosities that may maraud across your play area. For the decks that plan on going long, I would recommend at least three.
3. Thoughtseize. Not Inquisition of Kozilek. Think about it for a second—your only true removal spell kills permanents that cost three or less. Why would you want to place a similar restriction on your pinpoint discard spell? Are you so eager to lose to Batterskull, Jace, Time Spiral, Ad Nauseam, Goblin Ringleader, Sneak Attack, Hive Mind, and Emrakul that you refuse to pay two life to have the option of beating those cards? I would play my fourth Thoughtseize before I play my first Inquisition. Before I put either in my deck, though, I would want to make sure that I want that many discard effects in it.
The Threat and Counter Suites
There is a predictable way of understanding the counterspell suite that each deck packs.
If they have Shardless Agent, they can't play any zero-, one-, or two-mana counters, so they are very likely to have Force of Will. They're pricing into their deck a significant tempo loss in the form of Ancestral Vision, so Force of Will is the best way to hedge that bet. It blunts the card advantage upside, but it also stems the bleeding from the tempo loss downside.
If they have Delver of Secrets, they almost certainly have Daze and Force of Will, as a Delver deck is going to be primarily concerned with committing pressure to the board. This incentivizes them to find free modes of interaction, thus Daze and Force of Will. Since they are planning on ending the game quickly, Force of Will's downside isn't of great concern. Put another way, if you see someone with Delver of Secrets and Ancestral Vision in their deck, they're doing it wrong. You are most likely to find Tombstalker in a Delver of Secrets deck.
If they have Snapcaster Mage, they do not have Daze. Snapcaster and Daze don't work well together—you can't flashback a spell for its alternate cost, and paying four mana for a 2/1 and a Force Spike is quite a poor rate. It is possible but unlikely that a Snapcaster deck has Spell Pierce, as that is a natural fit for the card. They will have Force of Will because Bob/Snapcaster decks can create enough card advantage to give some back with Force. They also have a strong incentive to protect Bob with free countermagic, but they don't want to play Daze because bouncing a land is bad with Snapcaster and, again, Daze isn't a card you want to flash back.
Dark Confidant decks are either Snapcaster Mage decks or Jace, the Mind Sculptor decks but never Delver decks. While both Delver and Bob are powerful cards, Delver of Secrets wants you to build your deck with short-term payoffs in mind. Having a Bob reveal a bunch of Force Spikes in a long game isn't the most optimal use of the card.
The presence of Liliana of the Veil is a tipoff that Force of Will might not be in the maindeck. Liliana and Force of Will operate on conflicting axes—one wants cards in hand, the other doesn't—and Liliana is a very powerful card in the BUG midrange/control mirrors that will be popular come Saturday.
The Mana Base
BUG decks play anywhere from 20-23 lands. Delver decks play 20, the Snapcaster/Bob versions play 21-22, Shardless versions play 22, and planeswalker-heavy versions play 23.
4 Wasteland: Every non-Shardless Agent build I have seen plays four Wastelands—yes, even the ones that have maindeck Jaces. Wasteland is too good to not play. It's a good defensive tool against Creeping Tar Pit, it buys time for your land-heavy hand to draw action, it randomly mises a percentage of games against land-light opponents, and it keeps Deathrite Shaman active for longer. It's a key component of the Wasteland / Life from the Loam angle of attack in control mirrors, an angle that is particularly effective in three-color good stuff mirrors where both decks have few (if any) basic lands.
9-11 Fetchlands: If you want to play a turn 2 Liliana off of Deathrite Shaman, you need to always have the fetchland. Don't skimp.
6-7 Dual Lands: In general, the configuration is three Underground Sea, two Bayou, and either one or two Tropical Island. Tropical Island is the worst of your duals to naturally draw, as it doesn't cast Hymn to Tourach or Liliana of the Veil. Your first two turns will ideally involve Underground Sea and Bayou since that pairing casts all of your low-curve spells.
0-2 Basics: Island doesn't help cast Abrupt Decay or Hymn to Tourach. Swamp doesn't cast Brainstorm or Ponder. You're always going to present a Wasteland target if you have two lands in play, so playing basic lands genuinely confuses me. For those of you who still think basics are good against Wasteland, here's a mental exercise:
You have two of the following lands in play. Pick any:
You just passed your second turn. Your opponent puts a Wasteland in play. Can they activate it? If they can't, can you cast your spells with your lands? If they can, can you cast all of your spells when you draw a (new) second land? If not, how much good is that Swamp or Island doing you? Is it there for the moral victory? It's sure not casting all of your spells…
0-2 Utility Lands: In general, these are Creeping Tar Pits, although there is a good argument for including a Riptide Laboratory in the Snapcaster Mage deck. Having an unblockable 3/2 that can't be Decayed is a big deal when people are trying to win by casting discard spells into planeswalkers. Creeping Tar Pit is just another reason to have all four Wastelands in your deck and to use them judiciously.
Every BUG sideboard looks fairly similar. There's the aggro section:
The combo section:
And the "everything else" section, where I'm fairly convinced people just play the cards that they want to play. Below, by the way, is my "cards that are very good that you aren't playing" section:
Really, Ghastly Demise is unplayable garbage. Disfigure is leagues better. It wins the Goyf wars you want to win, it kills Deathrite, it kills Lackey on the draw, and it kills Delver. Dismember kills Tombstalker and most Tarmogoyfs, which is more than most removal spells can say.
Ostensibly, these should be some kind of midrange trump, but some people go way too deep. The following is a friend's thought process while building a BUG sideboard with an eye toward the mirror, with my internal monologue interspersed:
"I want to be the guy with the planeswalkers, so I'm going to play a bunch of Jaces and Lilianas and end games with both of those in play."
So far, so good. Clear idea of what the end game looks like, the cards will help reach the desired game state, and they are powerful effects in a matchup defined by cards that trade one-for-one at a low rate.
"I also want to attack my opponent's mana base, so I'll play a Life from the Loam."
Still good—Loam is a very powerful way to attack three-color mirrors, as I said earlier.
This is where the thought process goes off the rails. People aren't exactly going to cut their Abrupt Decays, so boarding in a Grizzly Bear—even though it has a solid ability—isn't worth the slot unless you're also expecting a lot of Reanimator and Dredge. Beyond that, Scavenging Ooze isn't providing a new effect since you already have Deathrite Shaman to eat away at lands, creatures, instants, and sorceries.
Okay, now our plan is just disjointed. Are we playing defense or offense? What are we cutting for all of these sideboard cards? How are we playing all of these cards and not losing to Goblins or Thalia, Guardian of Thraben? While the pseudo-mirror is important, it's not the only matchup you're going to face in a tournament.
At least as important as that is the knowledge that you will board differently against different flavors of BUG. If they have Delver of Secrets, I don't want my Hymns, but I do want my Ghastly Demises and Dismembers. If they have Jace, I don't want non-Abrupt Decay removal, but I do want a lot of discard. You get the basic idea. There isn't one uniform sideboard plan for a generic opponent who put a Bayou and a Tropical Island into play.
Decks to Play if You Want to Beat BUG
Anything with Chain Lightning and Price of Progress. It can have Goblin Guides or Steppe Lynxes, but it should have a low curve, be able to kill a Deathrite Shaman on sight, and come out swinging hard. Abrupt Decay is pretty bad when it only ever kills one-drops, so forcing them to lose value with their removal is a step toward winning.
Also, I don't think I have ever witnessed a BUG deck in the history of Magic beat the card Price of Progress. That card is worth eight damage every time. It's disgusting.
For instance, I think Zoo is decently positioned again:
As low to the ground as possible. You don't want your Knight of the Reliquary or whatever to get Abrupt Decayed. Just get in a ton of damage in the first three turns and start peeling cards off of the deck and pointing them upstairs.
Thalia is better than Pridemage right now because you want to punish cantrip-heavy decks—the Miracle decks are getting pushed out by Abrupt Decay, meaning that cheap spells are the next frontier to hate on. Yes, your Bolts will cost more. No, it doesn't matter. Just keep attacking them. Nothing trades with a Deathrite Shaman or Dark Confidant or Snapcaster Mage, which is an important feature of the creature base. Goblin Guide would be a huge liability here.
I don't think Mindbreak Trap is worth playing over Gaddock Teeg, although I thought about it. You'd rather have a good slot against Terminus and Jace than against Empty the Warrens. Everything else is pretty obviously functional. Sylvan Library is for white control and combo matchups only, but it shines there.
The mana base is very straightforward. You only need two lands in play to make a super Wild Nacatl, all your lands cast Fireblast, and you want Steppe Lynx once you're playing twelve fetchlands. As I said before, basic lands are garbage, so this list doesn't play any.
If you're looking for a combo list that consistently beats BUG, I wish you luck. I've been working to find a good way through the tangle of discard spells, planeswalkers, and Deathrite Shamans, but I'm not completely convinced that there's an unfair deck with a positive BUG matchup. It's fairly obvious that Reanimator and Dredge are poor choices for an unfair linear, as Surgical Extraction and Deathrite Shaman have given huge swaths of decks access to cheap and effective graveyard interaction.
It's also important to not get beat by Abrupt Decay, so permanent-based combos like Painter/Grindstone—already weakened by the presence of Emrakul—are still poor choices. Hive Mind is a fine consideration once you see that angle of the metagame. I worked on the deck for a while in preparation for the Invitational but ended up playing five-color Storm instead. If I'd played Hive Mind, it would have been this 75:
This was developed back when winning the Show and Tell mirror was a major concern. Leyline of Sanctity was a fairly easy inclusion because Show and Tell decks suffer the most against discard. Jace and Vendilion Clique are there to be proactive solutions to blue decks' walls of countermagic, forcing them to play sideboarded games on this deck's terms. Ultimately, there were a few too many dead cards in the list, so I shelved it. Still, if you're looking at playing Hive Mind, I suggest this as a starting point.
And if you decide you want to slog through two days of grindhouse Magic, I have but one piece of advice for you:
Be polite, be professional, but have a plan to kill everyone you meet.
Good luck in Denver. I'll see you there!
@drewlevin on Twitter