Rathi Fiend is a uncommon Creature — Phyrexian Horror Mercenary card from Nemesis (NEM), collector number 68. Current market price: $0.23 (foil $3.69), TCGplayer market prices via Scryfall.
When this creature enters, each player loses 3 life. {3}, {T}: Search your library for a Mercenary permanent card with mana value 3 or less, put it onto the battlefield, then shuffle.