Nihil Spellbomb exiles their graveyard, which is relevant against Archaeomancer's recursion of instants/sorceries and generally disrupts their value engine while cantripping later. Arms of Hadar sweeps their small value creatures like Baleful Strix, Refurbished Familiar, and tokens generated along the way, which combos poorly for them if Ephemerate has already been used to double up ETBs. Spell Pierce is weaker against a deck with plenty of mana available by the time they're casting their payoffs, and Plunder the Trollshaws is too slow in this grindy value matchup, so both are trimmed for proactive disruption. Prioritize countering Ephemerate or the creature it targets to deny the double ETB value from Baleful Strix, Mulldrifter, or Refurbished Familiar.