In biology, a dichotomous key is useful for classifying items in the natural world so that when two biologists discuss an observed phenomena they can communicate with a common language and understand each other. For scientists, this allows them to distinguish between Canis lupus (gray wolf) and Canis lupus familiaris (domestic dog). In a game of Magic, you can use similar classification techniques to determine if your opponent is on Dredge or Tron based on their early plays. In fact, your opponent may communicate observable hints from as early as the first land they play to allow you to compartmentalize their strategy into certain distinct archetypes.

Learning to recognize these hints quickly can better help you plan your game around their strategy, and also conceal or even misrepresent your strategy via deckbuilding or early game decisions.

With the Pro Tour being Modern, I’ve chosen to create a key that includes common turn-1 lands that are played in the format, and give you some hints on how I would start to piece together what my opponent is playing. Obviously, if your opponent plays out a Darksteel Citadel, Vault Skirge, Mox Opal, Springleaf Drum, and Signal Pest, or suspends a Search for Tomorrow or plays Unclaimed Territory naming Merfolk, you don’t need a strategy article to decipher their game plan, so for the purposes of this article let’s assume that they did nothing besides play a land before passing.

Note: I’m ignoring theoretically possible options like Glimmervoid or Blinkmoth Nexus because it is unlikely that your opponent would keep that hand if it did not do anything else on turn 1.

The Fetchlands

The fetchlands are the best lands that are legal in Modern and are the most played as well, so I might as well start there. These lands do not telegraph your strategy as much as shocklands because if you are playing a 2-color deck, you can (and often should) play off-color fetches, and this form of misdirection may lead your opponent into thinking that you are playing something that you are not.

Green Fetches

My first thought when my opponent plays a green fetchland and passes the turn is R/G TitanShift. I begin to think that I want to play my hand as aggressively as possible. This means that I want to flash in a Snapcaster for no value, scry removal spells to the bottom with Serum Visions, play my creatures before my discard spells in Grixis Shadow, and plan to aim any burn at my opponent.

My instincts would say TitanShift because many decks with green fetches rely on turn-1 creatures in the form of Birds of Paradise, Noble Hierarch, Goblin Guide, etc. or discard spells off of Overgrown Tombs, and my opponent passed without doing anything. If my first instincts are wrong, I’ll find out soon if they were to fetch a tapped Breeding Pool/Overgrown Tomb/Temple Garden, or if they fetch a Sacred Foundry and Lightning Bolt me, and my actions are unlikely to be detrimental if I can then recognize their strategy on turn 2.

Any green fetch could be:

TitanShift
Infect
Elves
R/G Land Destruction
Bogles

Wooded Foothills:

Burn
Dredge

Verdant Catacombs:

4/5-Color Shadow
Classic Abzan
Classic Jund
Abzan Company
Classic Living End

Windswept Heath:

Classic Abzan
Abzan Company
G/W Company
Bant Spirits
Bant Knightfall

Misty Rainforest:

Bant Spirits
Bant Knightfall
U/G Merfolk

Blue Fetch

Blue fetchland and pass first makes me think Jeskai Control if it is a Scalding Tarn or a Flooded Strand. This means that I am not running out my Glistener Elf until turn 2 when I can protect it from Lightning Bolt, for example. If my opponent fetches up a basic Island to do anything, I am immediately on the alert for Blood Moon.

Death’s Shadow often plays a lot of blue fetches, but they have so many turn-1 plays in Serum Visions, Inquisition of Kozilek, and Thoughtseize that they do not usually keep hands without something to play for 1 mana. Look for the end-of-turn Fatal Push if they know that you are on a creature strategy or an end-of-turn Opt. Although Storm decks have recently moved away from a fetchland mana base, it is still possible that my opponent could play a version with fetches, but since they did not cast Serum Visions or Sleight of Hand I am less likely to expect this from my opponent.

Any blue fetch could mean:

U/W Control
Storm
Blue Moon
Grixis Control
Breach

Polluted Delta:

Grixis Shadow

Scalding Tarn:

Jeskai Control
Grixis Shadow
U/R Breach
Burn

Flooded Strand:

Jeskai Control
UW Control
Bant Spirits

White Fetch

White fetchlands are probably the most straightforward of all of the fetchlands. Because there is not a widely played base white-deck that plays fetchlands, you would not expect a deck to play Flooded Strand unless it wanted access to both blue and white, or Marsh Flats unless it wanted access to white and black. This is different from Infect or TitanShift, for example, which can play any green fetch or Grixis Control, which sometimes wants the 9th blue fetch. So if I see a white fetch, I am quick to put my opponent into one of these archetypes.

Flooded Strand:

Jeskai Control
U/W Control
Bant Spirits
Bant Knightfall

Windswept Heath:

Classic Abzan
Abzan Company
G/W Company
Bant Spirits
Bant Knightfall
TitanShift
Infect
Elves
R/G Land Destruction
Bogles

Arid Mesa:

Burn
Jeskai Control

Marsh Flats:

Classic Abzan
Mardu Pyromancer
Death’s Shadow
U/W Control

Red Fetch

Red fetches make me consider the consequences of my opponent playing burn spells. If my opponent is on Burn then I will want to preserve my life total as much as I can (unless I am playing Death’s Shadow). If I have more expendable creatures like Voice of Resurgence then I want to play them out first. If I am playing Storm, I would consider leaving up Remand for a potential Eidolon of the Great Revel from a Burn opponent, which is difficult to overcome in game 1 or for their Cathartic Reunion, which significantly slows down my Dredge opponent.

Any red fetch:

Burn
Dredge

Scalding Tarn:

Jeskai Control
Grixis Shadow
Blue Moon

Wooded Foothills:

TitanShift
Infect

Arid Mesa:

Jeskai Control

Bloodstained Mire:

Grixis Death’s Shadow
Mardu Pyromancer
Classic Jund

The Shocklands

The shocklands are what allow Modern to have 3-color decks. Unlike the fetchlands, these are often going to be a tell for what your opponent is playing because you will know if they have something to do with their mana (or just want to lower their own life total) by virtue of them playing the land untapped and passing the turn. Playing these lands tapped on the first turn can also be indicative of a slow hand or a slow deck.

Steam Vents

There is a reason that your opponent paid life to leave up mana on their first turn. If I am on the play, I would think Spell Snare or Lightning Bolt. If I am on the draw, I would think Opt.

Jeskai Control
Storm
Grixis Shadow
Grixis Control

Watery Grave

Untapped and I am thinking my opponent is on Grixis Shadow and wants to lower their life total. They may have an end-of-turn Thought Scour, Opt, or Fatal Push. They could also be on Grixis Control and have Spell Snare. If it enters tapped then I am leaning toward Grixis Control.

Hallowed Fountain

Unlikely to be coming into play untapped, but if it did I would expect Opt or Spell Snare (if I was playing first). I would anticipate Jeskai Control or U/W Control.

Breeding Pool

Tapped Breeding Pool is an uncommon start because most U/G decks have 1-mana accelerators such as Birds of Paradise and Noble Hierarch or 1-mana creatures such as Mausoleum Wanderer or Glistener Elf. Since these decks are often based on tempo, this start would suggest to me that my opponent’s hand is slower. I would be expecting U/G Merfolk, Infect, Bant Spirits, or Bant Knightfall.

Overgrown Tomb

Untapped and I am thinking 4/5-color Shadow and my opponent wants to lower their life total. I may also think they have Fatal Push, although I would not think they have any discard spells since they did not play any. This could also be a sign of classic Living End and that they want to cycle during my end step. Tapped and I would expect some B/G deck like classic Jund or Abzan.

Stomping Ground

Untapped and I would think my opponent has a Lightning Bolt or that they are on classic Living End and want to cycle. Tapped and I would think that they are playing TitanShift and have a turn-2 ramp spell and payoff in hand (or else they would have likely taken a mulligan).

Godless Shrine

Untapped and I think my opponent is playing 4/5-color Shadow and wants to lower their life total. I also think they have Lingering Souls in their deck. Tapped and I think my opponent is on Classic Abzan, although they could also be on Abzan Company with no 1-mana play.

Blood Crypt

Untapped and I think my opponent is on the Mardu Pyromancer deck with a Lightning Bolt or classic Living End and wants to cycle. This could also indicate Grixis Death’s Shadow, but Blood Crypt is often the worst land in the deck and it is unlikely that they’d keep this hand without a turn-1 discard spell. Tapped and I think my opponent is on Grixis Control and kept a land-light hand.

Sacred Foundry

I am thinking Lightning Bolt, whether it is out of Burn, Jeskai Control, or Mardu Pyromancer. If it enters tapped I am leaning toward Jeskai Control.

Temple Garden

Tapped and I think my opponent is on G/W Company with the combo already in hand since they kept a hand with no ramp. Could also indicate classic Abzan.

The Basic Lands

Despite being the narrowest lands, they can also provide you with a lot of information about your opponent’s strategy. In many Constructed mana bases, the basic land is the worst land in the deck because it likely does not let you cast all of your spells, so there must be something else about your opponent’s hand that led them to keep.

Island

Could indicate Storm, Merfolk, Grixis Shadow, Jeskai Control, Grixis Control, U/R Breach, or Mono-Blue Living End. This is the most diverse opening and I would need to wait for more information.

Mountain

Burn
Mardu Pyromancer
U/R Storm
Dredge
Grixis Control
Jeskai Control

Plains

Humans
Death and Taxes
B/W Eldrazi
U/W Control
G/W Company
Jeskai Control

Forest

G/W Company
Big Tron
TitanShift
Classic Abzan
Classic Jund
Elves
Classic Living End

The “Other Lands”

Many of these lands from your opponent are so rarely played that there is only one likely option.

Copperline Gorge

Dredge
Classic Living End
Classic Jund
Burn

Gemstone Mine

Dredge
Ad Nauseam
Bloomless Titan

Celestial Colonnade

Jeskai Control
U/W Control

Urza’s Mine/Urza’s Power Plant/Urza’s Tower

Eldrazi Tron
Classic Tron

Sanctum of Ugin

Classic Tron

Blackcleave Cliffs

Dredge
Classic Jund

Razorverge Thicket

Elves
G/W Company
Bogles
G/W Tron
Abzan Company

Blooming Marsh

Classic Abzan
B/G Midrange
Living End
B/G Tron

Botanical Sanctum

Lantern Control
U/G Merfolk
Amulet Titan
Bant Spirits

Horizon Canopy

Humans
G/W Company
Elves
Bogles

Seachrome Coast

Humans
Ad Nauseam
U/W Control

Valakut, the Molten Pinnacle/Sheltered Thicket/Cinder Glade

TitanShift

Inspiring Vantage

Burn

Shivan Reef/Spirebluff Canal

Storm

Eldrazi Temple/Sea Gate Wreckage/Ghost Quarter

Eldrazi Tron

Darkslick Shores/Inventor’s Fair/Academy Ruins/Llanowar Wastes/Spire of Industry

Lantern Control

Tolaria West

Mono-Blue Living End

Dakmor Salvage

Dredge

Ancient Ziggurat

Humans

Urborg, Tomb of Yawgmoth

8-Rack

Radiant Fountain/Slayer’s Stronghold/Sunhome, Fortress of the Legion/Temple of Mystery/Crumbling Vestige/Aether Hub/Khalni Garden

Bloomless Titan

Yavimaya Coast/Brushland/Adarkar Wastes

Bant Eldrazi

Temple of Deceit/Temple of Enlightenment/Dreadship Reef/City of Brass

Ad Nauseam

Raging Ravine

Classic Jund

Shambling Vents

Classic Abzan
B/W Eldrazi

Creeping Tar Pit

Grixis Control

Oboro, Palace in the Clouds/Minamo, School at Water’s Edge

Mon0-Blue Merfolk

How to Use These Perceptions to Your Advantage

When you are building Dredge or Burn, for example, you can use Scalding Tarns instead of Wooded Foothills to disguise your strategy. Scalding Tarns can evoke blue spells and can make your opponent think that you are on a different plan. Maybe your opponent has played three Jeskai Control opponents in a row and their brain will lead them to a mental shortcut that reaches the wrong conclusion when they see your Scalding Tarn and you pass the turn. If you are playing Storm, use Polluted Deltas if you are looking for fetchlands after Scalding Tarn.

The Polluted Delta may make your opponent think that you are on Grixis Shadow or Grixis Control.

An example of when I have used this strategy is back when everyone was playing B/G midrange decks. I changed my fetchlands in my U/G Infect deck to Verdant Catacombs and Wooded Foothills since they are functionally equal in that build. I ended up fetching a tapped Breeding Pool at my opponent’s end step and my opponent commented that they thought that I was on B/G-based on my turn-1 land and would have executed their scry on their Serum Visions differently with this information. Sure, this technique may only earn a small fraction of edge in a small fraction of matches, but as you play more matches versus more skilled opponents, every small fraction of a small edge can matter.

Another way to use the information in this article to your advantage is when playing online. You could forego your “F6 value” by not fetching until their end step to conceal information. If all you care about is maximizing your win percentage, then that is likely the optimal time to retrieve your land.

What other decks or deck identifiers in Modern did I miss from my key? What other tells do you think can be picked up on early in a match that helps you plan your strategy? Share your comments below!