Nor Zael, Nivmagus

Prowess
Whenever you cast an instant or sorcery spell,
untap Nor Zael, Nivmagus.
{1}{u}{r}, {t}: Reveal cards from the top of target
library until you reveal an instant or sorcery card.
Exile it. You may cast that spell as long as it
remains in exile, using mana of any color to do
so. Then shuffle targeted library.