Eldrazi is a colorless-heavy ramp-aggro deck built on mana acceleration (Lotus Petal, Ancient Tomb, Eldrazi Temple), Chalice of the Void, and big colorless threats like Reality Smasher and Thought-Knot Seer. Consign to Memory is outstanding, it can counter any of their colorless spells (including the creatures themselves and Chalice) for just {U}, and it also answers triggered abilities like Thought-Knot Seer's enter trigger. It has mana value 1, so a Chalice of the Void set on 1 will counter it, but a Chalice set on 2 will not touch it. Erode handles their biggest threats regardless of size, though Sire of Seven Deaths' ward costs 7 life and Reality Smasher will counter it unless we discard a card. The basic-land tutoring downside is minor since we want them off the battlefield fast. Force of Negation is weak since their deck isn't built around one key noncreature spell to Force away, and Stifle is narrower than Consign to Memory here: it can hit triggers like Thought-Knot Seer's and Wastescape Battlemage's or Eye of Ugin's activation, but Consign covers those same triggers and the spells themselves. Keep Wasteland and Swords to Plowshares in, since Wasteland is strong against their nonbasic manabase (watch for Petrified Hamlet naming it) and Swords answers their big creatures.