This makes a difference more often than you might think: enabling the War Economy deck archetype I explored in a recent article, extra-turns decks, and anything which tries to partially or fully combo on opposing turns
Doing that again with rebound for no additional mana is just incredible, and the total package only asks you to invest a single white mana
Notably, you can't cast Archon of Emeria and then cast another spell during the same turn
The primary win condition is smashing face for commander damage, making her stronger with equipments and auras, with the help of some big trampling creatures
Offering a 2 energy cost for a powerful attack as long as your bench is full
Then, when they play their first game, Johnnys Combo goes off before they have a chance to cast even one of their high mana value creatures