Xiao Li, the Mortal Phoenix

When Xiao Li, enters the battlefield, search
your library for an instant card with converted
mana cost 2 or less and exile it. Put a flame
counter on it, then shuffle your library.
Whenever you cast a spell you may pay {x}
where X is the converted mana cost of a card
in exile with a flame counter, if you do cast a
copy of that card without paying its mana cost.