Erode is a clean Instant answer to Tamiyo, Inquisitive Student or Quantum Riddler that lets them fetch a basic, which is reasonable against their nonbasic-heavy Tundra/Island manabase. Containment Priest adds another efficient flash body that can trade with their small threats and isn't vulnerable to their Stifle since it's a static replacement effect, not a triggered ability. This is largely a fair creature-based mirror decided by efficient removal and tempo, so we keep our full Swords to Plowshares/Solitude/Skyclave Apparition suite and Thoughtseize to strip their Teferi, Time Raveler or key countermagic. We trim slow equipment pieces that don't impact the race against their proactive clock.