Izzet Prowess wants to go fast and race through combat damage from Dragon's Rage Channeler, Monastery Swiftspear, and Slickshot Show-Off; you need cheap interaction that kills their small creatures before they snowball. The extra Unholy Heat is excellent since delirium is easy for you and 6 damage cleanly answers anything they play, while Warping Wail exiles their 1-toughness threats (Monastery Swiftspear, Dragon's Rage Channeler pre-delirium) or counters a key sorcery. Firespout as a one-sided-ish sweeper for 3 to non-flyers wipes their whole board when they overextend. Vexing Bauble comes out since most of their removal (Lightning Bolt, Lava Dart) and card draw (Preordain) is paid for with real mana, so it rarely counters anything; Writhing Chrysalis is too slow against a deck built to kill you before turn 5.