Jeskai Ephemerate leans on fragile value creatures like Augur of Bolas, Murmuring Mystic, and Archaeomancer, so Horrific Assault lets us snipe these off with our bigger creatures before they generate repeated value through Ephemerate loops. Temur Battle Rage is risky against a deck holding up Counterspell and Dispel, since a countered attacker wastes the pump, so we trade it out for more reliable removal. We keep our ramp and core threats since this matchup rewards proactive pressure before their card advantage engine and Skred (which scales with snow permanents, and they run several) can stabilize the board. Focus on closing the game quickly while punishing their small creature bodies.