Duress proactively strips Counterspell, Snuff Out, or Spell Pierce before you commit your sacrifice engine pieces, which is vital against a deck full of efficient interaction. Go for the Throat cleanly answers Murmuring Mystic and Thorn of the Black Rose, both of which are nonartifact creatures. It can't target Baleful Strix because Strix is an artifact creature, so leave Strix to Cast Down and your other removal. Nihil Spellbomb does little against Grixis Control's gameplan, which is built on counterspells, removal, and card draw rather than graveyard synergies, so cut it along with slower value spells for more proactive disruption. Play around open mana for Counterspell and try to bait out their removal with lower-impact threats first.