UB is a tempo-cantrip deck with Force of Will and Thoughtseize but limited ways to interact with a resolved threat, similar to the Dimir Tempo matchup but slightly lower to the ground. Ancient Tomb comes in over Lotus Petal for repeatable, sustained acceleration to jam your reanimation spells ahead of their countermagic. Lead with Thoughtseize and Unmask to strip Force of Will before committing Animate Dead or Reanimate, since once your threat resolves they have almost no follow-up outside of a sideboarded Fatal Push or Barrowgoyf race. Griselbrand's lifegain is valuable to survive their early Stormchaser's Talent/token pressure while you set up.