WUBG relies on small creatures like Narcomoeba, Bloodghast, and Exhibition Tidecaller to fill the graveyard and enable Prized Amalgam, so Pyroclasm is strong against their early board, though it won't stop recursion from the graveyard long-term. Weathered Runestone is the real answer to that recursion: with it out, Bloodghast, Narcomoeba, and Prized Amalgam can't return to the battlefield from the graveyard, and Otherworldly Gaze and Practiced Offense can't be flashed back. We leave Redcap Melee in the sideboard, because every creature they play is nonred and each cast would cost us a land. Monstrous Rage and some Kumano Faces Kakkazan come out since this matchup rewards removal and racing over going wide with pump spells against a deck that can out-grind via recursion. Try to close the game quickly since their graveyard recursion engine only gets stronger over time; our own copies of The Legend of Roku and burn spells should prioritize pressure over long games.