Pulse of the Dross is a rare Sorcery card from Darksteel (DST), collector number 50. Current market price: $0.29 (foil $1.07), TCGplayer market prices via Scryfall.
Target player reveals three cards from their hand and you choose one of them. That player discards that card. Then if that player has more cards in hand than you, return Pulse of the Dross to its owner's hand.