Pretty standard list; two copies of Warping Wail maindeck to combat Titanshift, Humans, Storm, and Affinity, as well as two Mind Stone to smoothe out the deck amidst a plethora of decks running Blood Moon and Ghost Quarter/Field of Ruin effects at the moment. Testing without any copies of Karn Liberated in the 75 because against many of the most popular decks being played right now, Karn Liberated is pretty bad both pre- and post-sideboarding. Stubborn Denial, Remand, go-wide decks such as Affinity and Humans, and Blood Moon/Land Tax strategies keeping us below 7 mana are all reasons to put Karn Liberated to the side for now and focus on a more consistent performance of playing out powerful Eldrazi creatures with Eldrazi Temple game one. There's plenty of broken things to do with mana late game through Endbringer, Walking Ballista, and Ulamog, the Ceaseless Hunger. Cutting Karn improves matchups against the field overall while making any variation of the tron mirror more difficult.
As of Dominaria, the Warping Wails have been shifted to the sideboard to make room for two maindeck Karn, Scion of Urza. The card has performed extremely well in testing, often winning games where an early Blood Moon, Damping Sphere, or Ghost Quarter slowed us down; it also smoothed out cases of extreme flooding or games where I would have been stuck on 4 lands for way too many turns. The card quality in this deck is so high that upticking Karn is always going to end up bad for the opponent sooner rather than later.
Currently running the maindeck Sanctum of Ugin + Ulamog, the Ceaseless Hunger
package. Having removed Karn Liberated, both pieces add inevitability to our deck against midrange and control matchups and Ulamog is a tutorable answer to cards such as Ensnaring Bridge. So far I've been getting enough absurdly early (Turn 4-6) Ulamog casts for free wins as well as plenty of Sanctum Trigger --> Get Ulamog/another creature for a finisher to seal the game to make these two cards worth it.
I've been wanting as many Cavern of Souls and Ghost Quarters as can be fit in the deck lately. Multiple caverns feels quite important to be able to name Construct with the second one in a game or to play the second naming Eldrazi after the first has been destroyed or Spreading Seas'd; having as many copies of Ghost Quarter in the deck as possible helps against Affinity, GX Tron, and Titanshift, some of Eldrazi Tron's worst matchups, and pairs well with going back up to 2 copies of Surgical Extraction in the sideboard. In order to make room, I've cut Sea Gate Wreckage from the deck. In the massive majority of games, the game will be decided before we get to a board state where Wreckage takes it over. The games where Wreckage becomes a factor are so few and far between, and ultimately I think it's best to choose between it and Sanctum of Ugin for a flex-slot rather than trying to fit both in. If I had no Ulamog and no Sanctum in the deck, they would be replaced with a third Endbringer and a Wreckage. As of Dominaria, when Scion of Urza was put in the deck, the need for Sea Gate Wreckage is significantly less as our hand is empty much less often.
I've added 1x Spatial Contortion to the sideboard; I think it is time to add additional removal for all of these creature decks to trade 1-for-1. Dismember has a bit too much downside in the life loss to want 3 or 4 copies and Warping Wail is obviously limited in which creatures it can target, Spatial Contortion fills that additional removal role as well as can be done in colorless. Creatures in the 2-3 toughness range are a higher priority against the current popular decks. Goblin Electromancer, Leonin Arbiter and other hatebears, Spell Queller, and any of affinity creatures are where Contortion is best. Due to the abundance of graveyard decks at the moment (RB Hollow, Storm, Living End, Vengevine/Bridge, Dredge, and Jund to a lesser extent), there is much need for Grafdigger's and Relics in the side, and I'm also currently playing with 1x Surgical Extraction to try and interact with Bridge from Below and Dredge outside of relic. There are flex spots in the sideboard that can be used for graveyard hate or spot removal or even All is Dust/Ugin, that is dependent on the meta and what decks you want to beat post-board.
