Primordial Gnawer is a common Creature — Insect Horror card from The Lost Caverns of Ixalan (LCI), collector number 114. Current market price: $0.18 (foil $0.24), TCGplayer market prices via Scryfall.
When this creature dies, discover 3. (Exile cards from the top of your library until you exile a nonland card with mana value 3 or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)