Mono-Green Eldrazi wants to ramp into Emrakul, the Promised End and Devourer of Destiny and flood the board with Eldrazi Spawn tokens, so Wrath of the Skies comes in as a scalable sweeper that can wipe their board of small creatures and tokens for a modest energy payment. Consign to Memory is excellent against their many colorless spells and against triggered abilities such as the cast triggers on Emrakul, Devourer of Destiny, and Sowing Mycospawn. It counters colorless spells such as Devourer of Destiny, Basking Broodscale, or Kozilek's Command, but it cannot hit green spells like Malevolent Rumble or Ancient Stirrings, and activated land abilities are not valid targets since those are activated, not spells, so it mainly answers their big colorless spells and cast triggers. Quantum Riddler and Flickerwisp are weaker here since they don't interact with the opponent's game plan and do little against a deck planning to go over the top. Keep Solitude and Fatal Push in: Fatal Push answers Basking Broodscale, and Solitude can exile a resolved Devourer of Destiny, though its exile trigger happens on cast, so Consign to Memory is the way to stop that.