This Eldrazi combo deck's engine leans heavily on colorless permanents and triggered abilities (Blade of the Bloodchief's counter trigger, Basking Broodscale's token-making trigger, Glaring Fleshraker's triggers), making Consign to Memory a premium answer that can counter one of those triggered abilities or stop a colorless spell like Devourer of Destiny, with replicate letting it interrupt the combo chain repeatedly in one turn. Note that Eldrazi Spawn tokens do not come only from triggers: Malevolent Rumble is a green sorcery that creates its Spawn as it resolves, so Consign to Memory cannot counter it. Sacrificing a Spawn for mana is also a mana ability and cannot be countered. Nihil Spellbomb exiles their graveyard to blunt the cards Malevolent Rumble puts there, which matters for Emrakul's cost reduction and Shifting Woodland's delirium, and it can be sacrificed proactively before they combo off. Spell Pierce, Faithful Mending, and one Preordain are cut since they're too passive to interact with the actual combo turn, where instant-speed answers to triggers matter far more.