Who said you needed fancy dual lands or colored spells to win in Legacy? The Eldrazi, lock pieces, and the fastest mana outside of Vintage make Eldrazi Post one of the top decks in the format.
We’ve learned to respect an early Thought-Knot Seer in Standard, Modern, and now all Eternal formats as well. A 4/4 body is perfect for evading cards like Lightning Bolt, and Thought-Knot is large enough to threaten to end the game in short order. The information just from seeing your opponent’s hand is important, but being able to exile a card to disrupt their game plan is a big swing. Thought-Knot Seer contributed to the Eye of Ugin banning in Modern thanks to how often it hit the board on turn 2, and Legacy Eldrazi Post has the tools to do that consistently.
The rest of the creatures aren’t nearly as cheap as your 4-mana Thought-Knot option. The next creature on the curve—well, it’s a tie… between 3 different creatures—that all cost 10 mana. Ulamog, the Ceaseless Hunger will be the best of the bunch more often than not. Exiling two permanents is often enough to put a game out of reach, and a 10/10 indestructible creature that starts exiling massive chunks of their library when it attacks will finish the job. Kozilek, Butcher of Truth and Kozilek, the Great Distortion provide you two different yet similar options for filling up your hand and ending the game. Butcher of Truth gives you that beautiful cast trigger of drawing four cards, plays well against countermagic, and ends the game with its size and annihilator trigger. The Great Distortion gives you a bunch of cards as well, and can even counter combos or sweepers with its activated ability.
The curve somehow doesn’t stop there. You have Emrakul, the Promised End to wreak havoc on the opponent. Getting to take their next turn is usually enough to empty their hand and most of their board, and Emrakul ends the game shortly after. You don’t even have many different card types in your deck, nor do you have ways to get them into the graveyard, but this deck doesn’t mind just casting a 13-drop.
That mana ramp starts with your lands, often referred to as Sol lands thanks to their Sol-Ring-esque ability. Ancient Tomb and City of Traitors both tap for 2 mana with some downside. Eldrazi Temple and Eye of Ugin both help reduce the cost of Eldrazi in your deck.
Beyond that, you also have access to Cloudpost. With Cloudposts, Glimmerposts, and Vesuvas to copy them, you can start ramping without casting a single spell. The Cloudposts enter tapped, but getting 3 out in the early turns either the natural way of with Vesuva’s help will give you access to 10+ mana on turn 4.
This deck has plenty of actual ramp spells as well to help you reach double-digit mana early and consistently. Grim Monolith is the best at this, as you have plenty of ways to turbo it out and it will start producing heaps of mana. Basalt Monolith and Thran Dynamo are a bit more expensive to cast but will have a similar impact on the game. Not untapping isn’t a huge drawback when they’re being used to cast spells that end the game. But if you’re like me and you want your mana every turn, or if you just want another spell that will ramp you even further, you have three copies of Voltaic Key to untap your mana rocks.
As far as lock pieces go,, you have Chalice of the Void that you can cast on 1 and Trinisphere to completely lock someone out of the game. A turn-1 Sol land, Grim Monolith, Trinisphere is game over against almost any opponent who doesn’t have Force of Will plus blue card at the ready.
Sometimes permanents do sneak their way onto the battlefield, but Ugin, the Spirit Dragon can clean them all up. Whether it’s enchantments or creatures, Ugin can sweep the opponent’s board without touching any of your colorless permanents. Ticking up can take out a Jace, a medium-sized creature, or just start hitting the opponent. For additional fun, you have All is Dust, a perfect one-sided sweeper that is further aided by Eldrazi Temple and Eye of Ugin.
Eldrazi Post can quickly ramp out the biggest threats in the history of Magic with plenty of disruption and sweepers to keep the game under control. All of this accelerated power makes it a premier threat in Legacy!