Mass Diminish is a rare Sorcery card from Commander 2019 (C19), collector number 10. Current market price: $0.95, TCGplayer market prices via Scryfall.
Until your next turn, creatures target player controls have base power and toughness 1/1. Flashback {3}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)