Doomsday wins by assembling a five-card pile and closing with Thassa's Oracle when their library is empty, a plan Thoughtseize and Duress protect by stripping our interaction first. Leyline of Sanctity, put onto the battlefield for free from our opening hand, makes us immune to that discard entirely, forcing them to durdle into their kill without disrupting us. The extra Unmask lets us proactively strip their Doomsday or a counterspell protecting their combo turn, since we're the ones racing to close the game before their pile comes together. Bridge from Below does little against a deck with no removal to trigger it off combat, so we trim copies for the discard package.