Assert Authority is a uncommon Instant card from Mirrodin (MRD), collector number 30. Current market price: $0.33 (foil $3.70), TCGplayer market prices via Scryfall.
Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.) Counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.