Kayâ rEn, The Conjurer

Kay’rEn, The Conjurer is all colours.
Before you begin the game name a card.
Kay’rEn, The Conjurer's casting cost is
equal to that card's casting cost plus {1}.
When Kay’rEn, The Conjurer enters the
battlefield conjure the chosen card as if had just
been played then exile Kay’ren, The Conjurer.
... infinite potential.