Terrageddon wants to resolve Armageddon after building an advantage with Weathered Wayfarer and Sylvan Library, so Annul is a good fit here: it can counter Sylvan Library (their four copies are the main targets), Mox Diamond, or Seal of Cleansing on the stack, which is useful disruption against their card advantage and acceleration. Chain of Vapor can bounce a problematic nonland permanent like Terravore, Werebear, or Weathered Wayfarer for tempo, but it can't target lands, including an animated Treetop Village or Mishra's Factory. Smother stays in, since Terravore (mana value 3), Werebear (mana value 2), Wild Mongrel, and Weathered Wayfarer are all within its range. Sickening Dreams costs cards you need to rebuild after Armageddon, so it is trimmed. Prioritize card advantage and countermagic to out-grind them through the land destruction plan.