UBR is a grindy control-midrange deck full of card advantage (Deduce, Fable of the Mirror-Breaker) and flexible removal like Indomitable Creativity, so resilient incremental threats beat all-in payoffs. Elder Gargaroth is excellent: at 6/6 it shrugs off their burn (Fiery Impulse and Volcanic Spite deal only 2-3 damage), and it generates a Beast, life, or a card each time it attacks or blocks. Reclamation Sage gives you proactive value by destroying Fable of the Mirror-Breaker (as a Saga or after it flips) and artifact targets like the Mite tokens from Mirrex and the Clue and Treasure tokens they make. Cut Craterhoof Behemoth and Titan of Industry: they are expensive and slow against a deck with counterspells and card flow, and a single big threat can still be answered by Indomitable Creativity or bounced by The Theorist, Jace Beleren. Going wider with sticky value creatures is safer.