Billowing Shriekmass is a uncommon Creature — Spirit card from Foundations (FDN), collector number 56. Current market price: $0.14 (foil $0.29), TCGplayer market prices via Scryfall.
Flying When this creature enters, mill three cards. (Put the top three cards of your library into your graveyard.) Threshold — This creature gets +2/+1 as long as there are seven or more cards in your graveyard.