UBG Reanimator wants to discard or ritual into Griselbrand, Atraxa, or Archon of Cruelty and reanimate them cheaply via Reanimate, Animate Dead, or Shallow Grave, so Grafdigger's Cage is crucial: it stops creatures from entering the battlefield unless cast, shutting down their entire reanimation plan. Consign to Memory can counter any colorless spells or triggered abilities they rely on. Omniscience is far too slow against a deck that can cheat out Griselbrand or Atraxa on turn 1-2, and Flusterstorm has no profitable storm targets against this non-storm combo deck, so both are cut in favor of proactive hate.