Jeskai Ephemerate is a value-control deck built around Mulldrifter, Augur of Bolas, and Ephemerate loops protected by Counterspell and Dispel, so Duress proactively strips a counterspell or a key piece like Ephemerate before we commit threats. Nihil Spellbomb has little upside here since their engine isn't graveyard-dependent (Archaeomancer returns spells to hand, not via graveyard shenanigans beyond normal casting), making it a weak inclusion. Keep the full removal suite (Cast Down) since their creatures like Murmuring Mystic and Augur of Bolas are relevant to kill before tokens or card advantage pile up. This is a grindy matchup where disrupting their proactive plays with Duress and sequencing around open blue mana matters most.