Activate Scroll Rack by paying ({1} magic symbol) and tapping it, exiling Worldfire from your hand face down, then causing you to draw one card and put Worldfire on top of your library.
Cast any sorcery spell from your hand by paying its mana cost.
Possibility Storm and Guttersnipe trigger.
Resolve the Possibility Storm trigger, exiling the sorcery spell, then exiling Worldfire from the top of your library and casting it without paying its mana cost.
Guttersnipe triggers, dealing 2 damage to each opponent.
Resolve Worldfire, exiling all permanents, all cards in all hands and graveyards, and setting each player's life total to one.
Resolve the Guttersnipe trigger from step 3, dealing 2 damage to each opponent.
Each opponent loses the game due to having less than zero life.