Eldrazi Tron has risen to Tier-1 status thanks to its consistent domination in recent Modern tournaments. The strength of the deck is being able to assemble its Tron lands and Eldrazi Temples in the early stage of the game to immediately start casting haymaker upon haymaker. It starts to snowball out of control usually by turn 2 Thought-Knot Seer or a turn 3 Karn, or sometimes summoning Ulamog, the Ceaseless Hunger by turn 4!
Despite its recent dominance in major tournaments, the deck is still beatable. In no particular order, here are some sideboard cards that can help you overcome the Eldrazi invasion.
Blood Moon
Pros: Eldrazi Tron decks are highly reliant on the big mana produced by their combination of lands. Turning these lands into Mountains will slow down the deployment of their threats while you execute your game plan. Cons: Experienced players will anticipate and play around this card. Drawing this card in the mid-to-late game may be too late already.
Fulminator Mage
Pros: This Stone Rain with legs greatly helps with the mana denial plan. You simply sacrifice it to disrupt the combination of Tron lands. What adds more value to the card is you can get it back from the graveyard via Kolaghan's Command or Liliana, the Last Hope's ability.
Cons: Not a good draw if the opponent has already assembled the lands they need. Turning off the Tron lands is gonna be a lot trickier.
Crumble to Dust
Pros: If this spell successfully exiles one of the Tron lands, you'll feel a bit safer knowing that the Tron lands will never assemble and just have to deal with the Eldrazi Temples. The exile effect also gives you the chance to peek into the opponent's hand and library, giving you valuable information on what their game plan is.
Cons: By the time you cast this spell, the opponent may have already assembled the lands they require. The exile effect loses its maximum value if more than one copy of the Tron lands is on the battlefield already.
Spreading Seas
Pros: This helps disrupt the combination of the Tron lands and lets you draw a card as well. If you are piloting a Merfolk deck, this will help you push your Islandwalk creatures through the big Eldrazi creatures in the way. If you are piloting a blue-based control deck, this'll help buy you time or turn off that Cavern of Souls that's preventing you from countering those Eldrazi creatures.
Cons: It only disrupts the land but the opponent can still use the land for mana. Drawing this card in the mid-to-late game may be too late already.
Ghost Quarter
Pros: This card can help you pick apart the opponent's manabase and deny them mana. This card does wonders alongside with Ramunap Excavator and Crucible of Worlds.
Cons: Depsite destroying their crucial lands, the opponent can still search for their basic lands. Also as mentioned before, drawing this card in the mid-to-late game may be too late already.
Tectonic Edge
Pros: Similar to Ghost Quarter, this helps with the mana denial plan. Upside is the opponent doesn't get to search a basic land to replace the destroyed land.
Cons: Downside of this card is the ability can only be activated when the opponent has four or more lands. Usually, the opponent already has their Tron lands assembled by turn 3, a turn too late.
Ancient Grudge
Pros: Artifact hate can help pick off the crucial artifacts from Eldrazi Tron. Viable targets are: Basilisk Collar, Mind Stone, Wurmcoil Engine, Chalice of the Void (as long as it isn't on 2 counters), Walking Ballista (they'll be forced to use the sacrifice ability for value), etc.
Cons: Not much value against Walking Ballista, Hangarback Walker and Wurmcoil Engine.
Kolaghan's Command
Pros: The versatility of this card simply shows how much value it can generate. Such plays you can execute are: Get back your Fulminator Mage from the graveyard, force your opponent to discard that Ugin, the Spirit Dragon they've been holding as their last card, destroy that pesky Basilisk Collar, or deal that last 2 damage to the dome.
Cons: Not much of a downside except for the last ability. The Shock effect on target creature or player is the least used ability in this match-up.
Stony Silence
Pros: Best artifact hate against this match-up. Stops Expedition Map, Mind Stone, Walking Ballista, Hangarback Walker and Ratchet Bomb just to name a few. Once this card hits the board, it is difficult to get rid off for the opponent.
Cons: Not much of a downside except for playing this card during the late game or opponent has a way to remove this from the battlefield.
Pithing Needle
Pros: The strength of this card is in its versatility in shutting down a specific card. It can stop abilities of the Planeswalkers to the artifacts to the creatures.
Cons: It can only stop one card. Opponents can play around this card and find another route to victory.
Path to Exile
Pros: Best spot removal for majority of the opponent's value creatures: Matter Reshaper (the "dies" ability will not trigger), Wurmcoil Engine (no tokens will be generated), Hangarback Walker (no tokens will be generated) and Ulamog, the Ceasless Hunger (it cannot be destroyed but it can be exiled).
Cons: Not much of downside except for giving the opponent a basic land.
Wrath of God
Pros: The best panic button when the opponent is ahead on board is to reset with a wrath effect. The Eldrazi creatures usually have a toughness of 4 or above and cards like Anger of the Gods or Kozilek's Return just won't cut it. Supreme Verdict and Damnation also serve the same purpose and can help you get out of a bind.
Cons: The only downside is this card becomes useless when you are ahead and already winning with your creatures. It'll just rot your in hands and never cast it.
Dusk / Dawn
Pros: All of the Eldrazi creatures in the deck have 3 power and above. The one-sided wrath effect of Dusk is backbreaking for the opponent while your army of 2 power and below survive. Plus, Dawn can help you rebuild your army.
Cons: Opponents can play around this card and not commit too much of their creatures on the battlefield.
Ensnaring Bridge
Pros: This can hold off the Eldrazi Tron's offense at bay. Their creatures are infamously known for having big power and toughness.
Cons: Proper management of cards in your hand to keep the creatures from attacking you. The opponent may play around this card and cast Walking Ballista for a huge amount of counters and ping you to death.
Thoughtseize
Pros: Hand disruption is essential from preventing the opponent in casting their haymakers. It also gives you information of the cards in their hand so you can evaluate how you will navigate in the upcoming turns.
Cons: Not much of a downside except for that turn you cast Thoughtseize and saw nothing but lands and still lost 2 life. Frown town.
Surgical Extraction
Pros: The effectivity of this card is similar to Crumble to Dust. It works best with Ghost Quarter, Fulminator Mage and other Stone Rain effects. You may target one of the Tron lands in the graveyard and get rid of the rest. On a bad day, you can still exile one of the other key threats in the opponent's graveyard knowing you won't have to worry about them topdecking that card.
Cons: Needs to combo with a Stone Rain effect in order for this card to be effective in the mana denial plan.
Leonin Arbiter
Pros: Simply stops Expedition Map from searching the key pieces to assemble the Tron lands. Works great with Ghost Quarter.
Cons: Some players can work around the pay 2 and still search their library.
Aven Mindcensor
Pros: Similar to Leonin Arbiter, this creature can hinder the search ability of Expedition Map. Its flying ability can pass through Eldrazi creatures gunking up the battlefield.
Cons: Sometimes the opponent gets lucky and finds that key Tron land in the top four cards of their library.
Intrepid Hero
Pros: This card is an all-star if left unanswered. Picking off their Eldrazi threats one-by-one is a joy to look at. Cons: It's weak power and toughness can easily be picked off by the activation of their Hangarback Walker.
Big Game Hunter
Pros: A cheap way to remove a big threat from Eldrazi Tron. This creature is mostly played by Collected Company decks and can be tutored to destroy a key threat on the board.
Cons: It's weak power and toughness don't make it much of a threat on the battlefield.
Shriekmaw
Pros: A cheap way to eliminate the big Eldrazi threats via Evoke. Works wonders when you can get this card back from the graveyard and reuse the Evoke ability. The Fear ability can also help penetrate through the Eldrazi threats standing in the way.
Cons: Sadly, the Evoke ability will not work on the artifact creatures: Walking Ballista, Hangarback Walker and Wurmcoil Engine.
Ceremonious Rejection
Pros: An absolute all-star that will counter all the spells of Eldrazi Tron. Nuff said.
Cons: A Cavern of Souls naming either Eldrazi or Construct can just ruin your day.
Disdainful Stroke
Pros: The scary threats of the Eldrazi Tron decks have the mana cost of 4 and above. This can counter the Eldrazi creatures, Planeswalkers and even All is Dust.
Cons: Similar to Ceremonious Rejection, a Cavern of Souls (naming Eldrazi or Construct) on the battlefield will just render this spell useless.