Sneak and Show wants to resolve Show and Tell or Sneak Attack to cheat Emrakul, Griselbrand, or Atraxa into play as fast as possible, so Chancellor of the Annex revealed from our opening hand taxes their very first spell, which can be the difference between them comfortably casting turn-one Ponder and being forced to find an extra mana. Its ongoing counter-unless-pay-1 ability also punishes every subsequent free spell they try to jam, forcing them to play around a tax they may not have mana for. We cut Throes of Chaos as it's our least efficient cascade spell and this matchup rewards disruption over incremental card selection. Race carefully: if they land Emrakul, remember our own Emrakul copies and Apex Devastator can still out-cascade them if we stick a big threat first.