Zaffai, The Second Fiddle

Magecraft —Whenever you cast or copy an
instant or sorcery, you may look at the top X
cards of your library, where X is that spell's mana
value. If you do, put one of those cards on top
of your library and the rest on the bottom of
your library in any order.
If X is 5 or greater you may put that card into
your hand instead.
If X is 10 or greater you may cast that card with-
out paying its mana cost.