Cheapest priced copy (Guilds of Ravnica): $1.49 at Card Kingdom, near mint, out of stock, their price list as of .
Etrata, the Silencer 
Legendary Creature — Vampire Assassin · 3/5 · Rare · Guilds of Ravnica · #170
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.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $1.49 to $3.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| GRN Guild Kit | 1 | Rare | — | $1.79 |
| Guilds of Ravnica | 170 | Rare | $1.49Out of stock | $3.49 |
| Guilds of Ravnica Promos | 170s | Rare | — | $3.99 |
5 rulings from Wizards of the Coast
- 5 October 2018If the player controls no creatures, Etrata's ability doesn't resolve. Etrata remains on the battlefield and its owner doesn't shuffle their library. The same is true if the target creature is an illegal target when Etrata's ability tries to resolve.
- 5 October 2018If Etrata's ability exiles a token creature, it won't count to determine whether three cards are exiled with hit counters.
- 5 October 2018If Etrata leaves the battlefield while its triggered ability is on the stack, it remains in its new zone and Etrata's owner shuffles their library.
- 5 October 2018Etrata's owner shuffles it into their library as the triggered ability resolves, regardless of how many cards are in exile or whether the player loses the game.
- 5 October 2018In a Commander game, if Etrata is your commander, you may put it into the command zone as its ability resolves. You'll still shuffle your library.