A Mysterious Creature

You can cover a face-down creature with this reminder card. A face-down creature that was cloaked or cast with disguise has ward {2}. (Whenever that creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)

Etrata, Deadly Fugitive

Deathtouch
Face-down creatures you control have "{2}{U}{B}: Turn this creature face up. If you can't, exile it, then you may cast the exiled card without paying its mana cost."
Whenever an Assassin you control deals combat damage to an opponent, cloak the top card of that player's library.