This matchup is a race against a two-card combo protected by a dense counterspell suite, so proactive disruption is far better than reactive answers. Bringing in the two sideboard Duress (on top of the mainboard copy) lets you strip Stifle, Vision Charm, Counterspell, or Foil before they can protect Phyrexian Dreadnought, clearing the way for Hermit Druid or Survival of the Fittest to close the game quickly. The two Xantid Swarm are excellent here: attacking with one shuts off the opponent's ability to cast any spells that turn, buying a critical window to combo off without fear of Counterspell or Stifle. Akroma, Palinchron, Psychatog, and Triskelion are clunky, expensive cards that don't advance the combo plan and are easily stranded behind counterspells, so they make room for the more proactive disruption. Prioritize discarding their counterspells and protection pieces (Duress cannot choose creatures), since the Dreadnought itself is much easier to race once it can't be defended.

Mono-Red Sligh relies on a horde of 1-2 toughness creatures (Jackal Pup, Goblin Vandal, Mogg Fanatic, Grim Lavamancer) so Pyroclasm sweeps their board cheaply while we rebuild with Survival of the Fittest. Duress does not hit their removal-heavy, creature-light plan efficiently and is better replaced. Battlefield Scrounger and Triskelion are too mana-intensive against a deck trying to burn us out quickly, so we prioritize efficient sweepers and speeding toward our combo kill instead.

Bring in the extra Duress copies to strip Sterling Grove, Enchantress's Presence, or Solitary Confinement before they lock the game up, ideally on turn one or two ahead of your combo turn. Ray of Revelation and Naturalize give you clean answers to Solitary Confinement and Opalescence, both of which can otherwise stop you cold or turn their permanents into blockers. Xantid Swarm's attack trigger stops them from casting spells on your turn, which can protect a Hermit Druid activation or a Survival chain from Swords to Plowshares. The cut cards are your clunkiest, most mana-hungry finishers (Akroma, Palinchron, Karmic Guide, Triskelion, Psychatog, Battlefield Scrounger) since this matchup is a race to assemble the graveyard combo rather than a fair creature fight. Keep Hermit Druid, Survival of the Fittest, and Unearth fully intact as your primary win condition.