Stiflenought is a fast combo-tempo deck centered on its key artifact threat, making Aura of Silence an effective inclusion from our sideboard. Aura of Silence taxes Phyrexian Dreadnought and destroys it on demand, while the swap trims two narrow graveyard-hate artifacts that do little against a deck with minimal graveyard synergy. Prioritize using Duress proactively on their combo enablers or counterspells before they can protect it, and hold Vindicate and Swords to Plowshares for the Dreadnought itself. Gerrard's Verdict and discard effects are excellent here since the deck is full of situational counterspells that become dead once discarded.