Sathriel, Angel of Deception

Flying, haste, shroud (This creature can't be the
target of spells or abilities.)
Whenever Sathriel, Angel of Deception attacks,
exile the top card of target opponent's library.
You may play that card this turn. If an instant or sorcery card was exiled this way, you may cast it without paying its mana cost. If you don't play
the exiled card, put a +1/+1 counter on Sathriel
and you gain 1 life.