The hugely popular trading card game Magic: The Gathering boasts a deep card pool and a huge variety of decks for the Standard, Modern, Legacy, and Vintage formats. Decks can be combo, aggro, control, or midrange across a variety of colors. Then there's Tron, one of the giants of the Modern format.
Tron has been a common sight in Modern for years, and it shows no sign of slowing down. It comes in Eldrazi, mono-green, and mono-blue variants, and arguably, the mono-green version is the most common and powerful in the Tron family. But this deck is not unbeatable. Other decks have all kinds of sideboard options for games 2 and 3 against this mana-hungry deck, many of them targeting Tron's unique manabase or the many activated abilities among its permanents. Which Modern-legal cards act as a good starting point for any anti-Tron sideboard?
10 Blood Moon
Newer Modern players will soon learn that Tron uses Ancient Stirrings, Sylvan Scrying, and Expedition Map to assemble Urza's Tower, Urza's Power Plant, and Urza's Mine as early as turn 3. Together, they can tap for seven colorless mana at once, making turn-three Karn Liberated and Wurmcoil Engine 100% feasible.
Beyond that, Tron can also crank out Ugin, the Spirit Dragon and make heavy use of Oblivion Stone. How to stop it? Play Blood Moon! For 2R, this enchantment converts all nonbasic lands into generic Mountains. No Karn Liberated was ever cast by paying RRR, after all. Just make sure that your own manabase can handle Blood Moon's effects, such as fetching for basic lands like Forests and Islands.
9 Alpine Moon
Here is another red moon that will give Tron players a real headache. This enchantment costs just one red mana, meaning a player can cast it and use its power long before Tron is assembled. On the draw, a turn-three Blood Moon might be too late if the Tron player got a Wurmcoil Engine out. Alpine Moon, by contrast, allows you to name a nonbasic land, then force that land to only tap for one mana of any color.
Those lands lose all other abilities and types, so Tron shuts right down! Given enough time, though, a Tron deck can play right through this, so be sure to go on the offensive!
8 Stony Silence
Let's take a short break from land attacks and think about activated abilities. Stony Silence is an enchantment costing 1W, and it disables all activated abilities of all artifacts, including mana abilities. Prismatic Star, Chromatic Sphere, and Expedition Map become useless for the Tron player, forcing them to assemble Tron through regular card draws (and that's definitely the slow way).
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Better yet, Stony Silence also neutralizes Oblivion Stone, so you won't have to worry about your board presence getting wiped out! Don't forget that some Tron builds include Walking Ballista, a powerhouse from Aether Revolt. But with Stony Silence out, that Ballista is now a simple beater, nothing more. It can't even give itself more +1/+1 counters!
7 Aven Mindcensor
White mana has another answer to Tron's tricky ways: a 2/1 flyer for 2W named Aven Mindcensor. This creature can attack planeswalkers at will, and more importantly, it won't allow an opponent to search their library beyond the top four cards!
This makes Expedition Map and Sylvan Scrying difficult to use correctly, with so few cards in the library to access. As a bonus, Aven Mindcensor has flash, so control players can leave mana up on their opponent's turn for either a counterspell, or the Aven.
6 Surgical Extraction
Now black mana gets a turn to attack Tron with this New Phyrexia sorcery. It costs one Phyrexian mana, so players might pay 2 life rather than B! The idea here is to destroy a Tron land or force the Tron player to discard one, then cast Surgical Extraction. This will scour the Tron player's hand, graveyard, and library alike for all other cards of that name, and exile them!
Once that is done, assembling Tron becomes absolutely impossible. In a pinch, a player can use this on a Karn or Wurmcoil Engine in the Tron player's graveyard to remove those threats for good. Surgical Extraction will work on anything except basic lands.
5 Damping Sphere
For the most part, sideboard tech against Tron means attacking Tron's unique manabase, and that trend continues with Damping Sphere. Fresh out of Dominaria, this two-drop artifact stops Urza lands cold. If any land (yours or theirs) is tapped for more than one mana, that land will only add one colorless mana rather than any other type or amount.
Even with the three Tron lands together, that manabase can only make three colorless mana, far short of what Karn or Ugin need. As a bonus, this also works against the Shadowmoor/Eventide filter lands such as Graven Cairns.
4 Ceremonious Rejection
Suppose your Tron opponent has a fully functional mana base, and either you were too late to disrupt it or you don't even have the means to. Don't despair! You still have options, and Ceremonious Rejection is a fine sideboard card in blue. For just U, this instant can counter a colorless spell, perfect against Tron.
This can neatly counter Wurmcoil Engine, all Karns, Ugin, and even Oblivion Stone. It can also counter Eldrazi such as Ulamog, but be aware that this counterspell won't stop a "when you cast" trigger. Early on, you might use this against Expedition Map, to indirectly disrupt a Tron manabase in the making. But be careful, in case the Tron player can play around that.
3 Ghost Quarter
These next two sideboard cards will target the Tron deck's manabase. Let's start with Ghost Quarter, a land printed in Dissention and printed again in Innistrad and other products. This land can tap for one colorless mana, but it can also tap to destroy a land. That land's controller may then tutor for a basic land (like with Path to Exile) and put it onto the battlefield.
This is great against Tron lands, and better yet, any deck can use Ghost Quarter. Hatebears decks in particular may also have Leonin Arbiter or Aven Mindcensor, making it more difficult for the Tron player to get a basic land out of the deal. Wicked!
2 Fulminator Mage
This is the final card on the list to attack lands. Fulminator Mage can sacrifice itself to destroy a nonbasic land, and yes indeed, it will target Tron lands with glee. The Mage doesn't even need to tap to do that; it just gets sacrificed.
With hybrid red and black mana, this 2/2 shaman is fairly easy to cast, and it can be reanimated to destroy a second land! Jund decks may side this in against Tron, and Living End decks take it a step further by having the Mage in the mainboard!
1 Pithing Needle
The list concludes with some tech against activated abilities, excluding mana abilities. This is a price-friendly artifact, costing just {1} to cast (so you can play it before Karn arrives). Name one card, and that card's activated abilities cannot be used at all!
If your colors don't support Stony Silence, this can work well against Expedition Map or Oblivion Stone, or even Walking Ballista. Better yet, it can target any Planeswalker, so Karn and Ugin will look pretty silly once this needle pokes them.