Estai, Simic Megantomancer

The first time each turn you cast a spell or activate an ability with X in its cost, double the value of X.
{x}{1}{u}{g}: Add X mana in any mixture of green and blue to your mana pool.
"To the Azorius, the whale's status as the largest mammal is a fact. To the Simic,
it's a challenge."