Dimir Midrange is grindy and full of small, sticky value creatures (Dream Beavers, Floodpits Drowner, Spyglass Siren) that Vicious Rivalry sweeps away cheaply. Null Summoner strips their best card from hand and threatens to cast it later, giving us a second discard-style effect against a deck full of card advantage engines. Disdainful Stroke answers Kaito, Enduring Curiosity, or Deadly Cover-Up. Awaken the Honored Dead and Winternight Stories are too slow against their own card advantage; we trim the maindeck Duress copies since Null Summoner covers that role better by also denting their late game.