Decree of Silence is a rare Enchantment card from Scourge (SCG), collector number 32. Current market price: $21.71 (foil $172.00), TCGplayer market prices via Scryfall.
Whenever an opponent casts a spell, counter that spell and put a depletion counter on this enchantment. If there are three or more depletion counters on this enchantment, sacrifice it. Cycling {4}{U}{U} ({4}{U}{U}, Discard this card: Draw a card.) When you cycle this card, you may counter target spell.