UBR is a control-combo deck packing counterspells like Make Disappear and card advantage engines like Deduce and The Theorist, Jace Beleren, so proactive discard with Thoughtseize strips their interaction or a key piece like Indomitable Creativity before they can use it. Fable of the Mirror-Breaker provides card selection and a resilient threat that survives their Fiery Impulse-style removal on the token side, giving us a grindy value engine to match their card advantage. Fatal Push is efficient removal for their early creatures like the Fable token itself. Lively Dirge and Umbral Collar Zealot come out since they're too passive against a deck that will out-value us with raw card draw if we don't apply pressure and disruption.