Terrageddon wants to land a big Terravore and blow up the board with Armageddon, so your removal spells and cheap threats need to close the game quickly before that reset happens. Crimson Acolyte's protection from red is only marginally relevant here since Terrageddon isn't primarily red, but it can activate for {W} to grant protection from red against their Pyroclasm or Earthquake from the sideboard, functionally saving a creature; still, treat this as a minor upgrade over the situational Cursed Scroll. Swords to Plowshares is excellent against Terravore since it exiles it before its power/toughness can grow further from lands hitting the graveyard. Otherwise keep the maindeck mostly intact, since your low curve lets you rebuild faster than they can after an Armageddon.