Fajara, the Storm Dancer

When Fajara, the Storm Dancer enters the
battlefield, you may search your library for an
instant card with converted mana cost 2 or less,
reveal it, and put it into your graveyard.
Whenever you cast an instant spell, you may
exile it. If you do, you may cast target instant
card in your graveyard with the same converted
mana cost as the exiled card without paying its
mana cost.