Etrata, the Silencer - 1 R GK1 Foil

Etrata can't be blocked.
Whenever Etrata deals combat damage to a player, exile target creature that player controls and put a hit counter on that card. That player loses the game if they own three or more exiled cards with hit counters on them. Etrata's owner shuffles Etrata into their library.

rare
Legendary Creature — Vampire Assassin
From the Magic: The Gathering set GRN Guild Kit.