The banning of Eye of Ugin in Modern cooled off the Eldrazi a bit from their time under the spotlight. Printing already undercosted creatures that could further have their costs reduced might have been a mistake! The Eldrazi haven’t actually left yet, as both Bant Eldrazi and Eldrazi Tron are real decks in Modern, but there’s another way to reduce the cost of these creatures.
Eldritch Evolution doesn’t “truly” reduce the cost of your creatures, but it allows you to tutor up whatever is best for the situation and spread the mana cost across multiple turns. Spending 3 mana to upgrade a creature by 2 mana is a net loss, but it allows for some awesome curve out potential. With some Eldrazi, some silver bullets in the main and sideboard, and some mana creatures, you can make Eldritch Evolution a potent spell. Throwing in a bunch of creatures that still get value after being sacrificed makes this deck a force.
The big Eldrazi are efficient threats. Thought-Knot Seer and Reality Smasher are more powerful than their casting costs suggest they should be, and they both feature excellent abilities. That your opponent cannot profitably interact with either is a huge boon, and curving Thought-Knot into Reality Smasher takes their answer and then finishes them off. This deck is more than capable of curving a mana creature into Eldrazi Temple to play a turn-2 Thought-Knot Seer. You’re also capable of double-Temple draws for accelerating your creatures out even without Evolution.
Noble Hierarch fixes your mana, accelerates you, and can even pump your attacking creatures. Birds of Paradise gives you mana creatures 5 and 6 so that you have the option of playing a turn-2 Evolution for a 3- drop, or cast a 3-drop from your hand.
Your 3-drops do serious work. Matter Reshaper has many ways to be cast on turn 2 thanks to 6 mana creatures and 4 Temples. When it dies, you get a free card either in play or in your hand, making it the perfect creature to sacrifice and evolve into a Reality Smasher. Kitchen Finks provides similar value as well as excellent insurance against aggressive decks. You have extra copies in the sideboard to really make those matchups favorable.
Voice of Resurgence gives you an excellent response to the uptick in blue decks in Modern while also being a fantastic creature to sacrifice to Evolution, leaving behind a giant threat even after going to the graveyard.
Eldrazi Displacer has the same benefits as Matter Reshaper in having lots of ways to cast it on turn 2, but you don’t get the same immediate value. Instead, you get the late-game potential of blinking your own creatures for their enters-the-battlefield triggers, killing opponent’s token creatures, or just tapping down blockers.
Your main-deck silver bullets start with the card advantage machine Eternal Witness. While Witness is a bit clunky as a 2-power creature for 3 that dies to everything, it makes your turn-1 mana creature, turn-2 Evolution an explosive opening. You can get Witness, return Evolution, and get a turn-3 Reality Smasher. Thragtusk provides another 5-drop to Evolution for when the time is right, and is another perfect combo card with Displacer. Orzhov Pontiff can be your best bullet against any deck going wide, token strategies, Infect, Affinity, or Empty the Warrens.
With 4 copies of the most efficient removal spells in Modern in Path to Exile, Eldritch Eldrazi has key interaction and a plethora of ways to accelerate into some of the best creatures ever printed!