Duress proactively strips Counterspell, Snuff Out, or Spell Pierce before you commit threats, which is key against a deck with heavy countermagic and efficient removal. Avenging Hunter's initiative trigger generates ongoing card advantage once it resolves, and Grixis has a limited set of answers for a 5/4: Snuff Out and Cast Down can kill it, but Cut Down cannot, since its total power and toughness is 9. Tithing Blade is weak since Grixis runs few creatures, so the edict hits a low-impact creature of their choice, and Campfire's slow lifegain doesn't matter in a long grindy matchup where card advantage is what wins. Keep Nihil Spellbomb mainboard since it replaces itself with a card when it goes to the graveyard (if you pay {B}) and can exile their graveyard, including Plunder the Trollshaws flashback.