Stiflenought wins by using Stifle to counter Phyrexian Dreadnought's triggered ability, putting an 12/12 into play on turn one or two backed by counterspell protection. Your discard suite — Cabal Therapy and Duress — is your most important tool; use Duress pre-combat to strip Stifle or Foil before you tap out, and use Cabal Therapy to follow up naming Counterspell or Foil once you've seen their hand. Diabolic Edict and Spinning Darkness are essential removal since Smother cannot kill a 12/12 Dreadnought; Spinning Darkness is especially efficient as a free spell when you have three black cards in hand. Withered Wretch comes out as it is largely irrelevant — their graveyard poses no threat and it is a weak body against their strategy. Knight of Stromgald and Nantuko Shade must apply pressure quickly to race before they assemble a protected Dreadnought.