Terrageddon's game plan is to fuel Terravore with dying lands and then resolve Armageddon to lock you out of the game, so your top priority is using Cabal Therapy and Duress aggressively to strip Armageddon before it resolves — naming Armageddon with Therapy is often correct even blind on the play. Engineered Plague naming Beast permanently neutralizes Terravore, their primary win condition, and turns off any future copies as well. Blastoderm is invaluable as a threat with shroud, making it immune to Swords to Plowshares and forcing real blocks from their aggressive creatures. Pernicious Deed cleans up Wild Mongrel, Call of the Herd tokens, and Weathered Wayfarer efficiently, while Vendetta and Bone Shredder provide additional removal for Terravore if Plague hasn't resolved yet. Dust Bowl is counterproductive here since you want to preserve your own mana base under land destruction pressure, and Phyrexian Furnace has no relevant targets, while Krosan Tusker's seven-mana casting cost is uncastable in this matchup.