Ensnaring Bridge is strong since our hand will often be low while Izzet Prowess tries to swing with small, efficient creatures like Monastery Swiftspear and Dragon's Rage Channeler. Chalice of the Void set to zero or one shuts off Mishra's Bauble, Mutagenic Growth, Lava Dart, and many of their one-mana spells that enable prowess and Cori-Steel Cutter triggers. Dismember kills most of their small creatures but is less necessary with Ensnaring Bridge locking the board down; we trim it to make room while keeping Kozilek's Command for flexible exile and card draw. Keep Trinisphere in the sideboard as a Karn, the Great Creator target to further tax their cheap spell-heavy plan.