Mono-Green Eldrazi wants to ramp into Emrakul, the Promised End and Sire of Seven Deaths, so High Noon limits their chains of cheap ramp and selection spells to one per turn (it limits us the same way) and buys time for our removal suite. Ashiok, Dream Render shuts off Sowing Mycospawn's land search and Urza's Saga's chapter III search while its -1 attacks their graveyard. Surgical Extraction can answer Emrakul once a copy hits their graveyard (for example off Malevolent Rumble), exiling the other copies from their hand and library too. Silence and Consult the Star Charts are the weakest here since Silence only buys one turn against a ramp deck and Consult digs too slowly against their proactive game plan.