Miricena, Wind Wizard

+1: Whenever you cast an instant this turn, add 1 red mana and 1 blue mana to your mana pool.
-4: Cast an instant or sorcery from your hand without paying its mana cost. At the end of your turn, return target spell from your exile to your hand
-7: Return all spells from your graveyard and exile to your hand. All cards returned cost 0 until end of turn.