With the new Eldrazi in Battle for Zendikar, we need to have the ability to exile an opponent's permanents before we can activate various actions that require the use of exiled cards. Any of the new spells is dead in the hand if your opponent has no cards in their exile zone.
The three Eldrazi spells in Rise of the Eldrazi are very powerful. All is Dust is best buddies with Devoid since all of the Devoid spells are colorless, even the ones that require colored mana as a casting cost.
Power 7 or greater is the threshold to protect all of your Eldrazi with Not of This World.
Hard casting for 8 is not easy, and here is where efficient use of Eldrazi Spawns and Scions is required. The question is if the new Eldrazi decks will be able to use both.
But even in the case of Eldrazi Conscription, annihilator places an opponent's permanents in their graveyard. What we need is efficient exilers. Titan's Presence as a 3-drop is very useful, you just need to have a big Eldrazi in your hand to make it work with most Eldrazis. Scour from Existence is a big unknown. It can be really good, I just don't know before playing a bunch of Eldrazi decks. "Exile target permanent" is up there with Griselbrand's "Draw 7 cards." Notice that you can exile lands. This is very important, especially if you are facing a late game Awakened land. I am calling these spells as must-haves for now.
Gruesome Slaughter can become a board wipe in no time. Eldrazi Devastator is here because I tried to get all images into pairs. Eldrazi Devastator passes the Not of this World test.
Link to Part 2