Spy Combo relies on a wide board of small mana-dork style creatures (Overgrown Battlement 0/4, Wall of Roots 0/5, Elves of Deep Shadow 1/1, Saruli Caretaker 0/3) and graveyard recursion via Dread Return to cheat Lotleth Giant or other big threats into play. Fiery Cannonade's 2 damage to each non-Pirate creature kills the small dorks like Elves of Deep Shadow, Quirion Ranger, and Gatecreeper Vine, disrupting their mana base before they can assemble a big Dread Return turn, though it won't touch the tougher bodies like Tinder Wall, Saruli Caretaker, Overgrown Battlement, and Wall of Roots. Nihil Spellbomb exiles their graveyard, which can strip away the creature cards Dread Return wants to bring back and remove Dread Return itself if it is sitting in the yard, and it also cleans up the cards a Balustrade Spy mills into their graveyard. Vampire's Kiss and Sazacap's Brew are cut since life gain and card draw don't address their board development, and this matchup is about disrupting their engine and racing before Lotleth Giant or Troll of Khazad-dum come down.