Screaming Shield is a uncommon Artifact — Equipment card from Ravnica Allegiance (RNA), collector number 239. Current market price: $0.22 (foil $0.21), TCGplayer market prices via Scryfall.
Equipped creature gets +0/+3 and has "{2}, {T}: Target player mills three cards." Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)