Mono-Black wants to strip your hand with Duress and Cabal Therapy while landing a fast Hypnotic Specter or Nantuko Shade, so your own Duress helps beat them to the punch, taking their Cabal Therapy or a key removal spell like Smother before it can hit your Survival of the Fittest. Swords to Plowshares is efficient, unconditional removal for Nantuko Shade or Hypnotic Specter, threats that are otherwise very hard for your deck to profitably block. Cut Elvish Spirit Guide, Squee, and Krosan Reclamation since your graveyard plan is somewhat symmetric with their discard theme and you'd rather hold real answers. Watch out for Withered Wretch, which can shut off your Hermit Druid and Unearth plans, so sequence around discarding it with Cabal Therapy if possible.