Archkleptomancer

Flash, Ward {2}
When Archkleptomancer enters the battlefield,
exile target noncreature spell. You may cast that
card for as long as it remains exiled, and you may
spend mana as though it were mana of any type
to cast that spell.
When Archkleptomancer leaves the battlefield,
the exiled card's owner may cast that card
without paying its mana cost.