Devlox Sphinx

Haste

When Devlox Sphinx attacks, defending player
searches your library for a card, then exiles it face
down. You name a card, then defending player
reveals the exiled card. If the exiled card is the
named card, Devlox Sphinx deals damage equal to
the exiled card's mana cost to any target and you
may play that card without paying its mana cost.
Otherwise, you may play that card until the end of
turn.