WUBG relies on recursive graveyard creatures (Bloodghast, Narcomoeba, Prized Amalgam) and graveyard-driven triggers. Doorkeeper Thrull is good against Prized Amalgam specifically, because Amalgam's return triggers off a creature entering and Thrull stops that trigger. It also gives you a flash flyer that can block their small bodies. Thrull does not stop Bloodghast, which returns on a landfall trigger when a land enters, and it does not stop Narcomoeba, which triggers from being put into the graveyard from the library. Thrull also turns off creature enter-the-battlefield triggers on your side, such as Fear of Missing Out. Sheltered by Ghosts exiles one of their key threats (like Altanak or a recurring Prized Amalgam) while giving your creature lifelink and ward {2}, which is valuable against a deck without much direct removal. Keep in mind the Aura itself has no ward and can still be answered by something like Witherbloom Command. Voldaren Epicure's small body and Fiery Temper's single-target burn are low-impact against their resilient recursive creatures that often come back anyway, so they're the easiest cuts. Prioritize denying their graveyard recursion engine over racing, since they can out-value you with repeated recursion if left unchecked.