Mono-Blue Terror's entire maindeck is blue with no artifacts, so Hydroblast and Blue Elemental Blast have no legal targets and must stay in the sideboard. Faerie Macabre exiles cards from their graveyard, directly attacking the instant/sorcery density that makes Tolarian Terror and Cryptic Serpent cheap, and can even discard itself for value if drawn late. Dispel counters their Counterspell or Spell Pierce for one mana, protecting your own card draw and Fog effects at a crucial moment. Cut Tangle, which matters less against a deck built around a few big evasive bodies rather than a wide attack, and trim Stream of Thought since filling their graveyard further is counterproductive.