Ara Rei, Reality Attuner

Flying, trample, hexproof
{x}, {t}: Exile target nonland permanent you own
with converted mana cost X. For as long as that
card remains exiled, you may cast it without
paying its mana cost.
Whenever a nontoken creature enters the
battlefield under your control, you may create a
token that's a copy of that creature, then sacrifice
that token.