Sneak and Show is a dedicated combo deck relying on Show and Tell and Sneak Attack to cheat out Atraxa, Emrakul, or Griselbrand, so free countermagic is essential. We already run 2 Force of Negation maindeck; the extra 2 copies let us consistently stop their Show and Tell or Sneak Attack even when tapped out, since Force of Negation only hits noncreature spells. Consign to Memory additionally answers their colorless Lotus Petal and any triggered abilities tied to their giant creatures. Back to Basics doesn't meaningfully slow a deck that can win off a single land drop plus Show and Tell, and Gandalf and Forth Eorlingas! are too slow to matter if they resolve a threat.