Devourer of Memory is a uncommon Creature — Nightmare card from Theros Beyond Death (THB), collector number 213. Current market price: $0.19 (foil $0.24), TCGplayer market prices via Scryfall.
Whenever one or more cards are put into your graveyard from your library, this creature gets +1/+1 until end of turn and can't be blocked this turn. {1}{U}{B}: Mill a card.