Terrageddon's listed deck is colorless-of-blue and runs no blue spells or permanents, so Pyroblast and Red Elemental Blast have no legal targets and stay in the sideboard. Their plan relies on Armageddon and land destruction (Wasteland, Rishadan Port) backed by Terravore, but your curve is low and your manabase (Barbarian Ring, Wooded Foothills, Bloodstained Mire plus Mountains) rebuilds faster off fewer lands than their green-white deck does. No sideboard changes are needed; your existing plan of fast, resilient damage already exploits a land-destruction strategy well, since you need fewer lands to execute your gameplan than they do.