Dulcet Sirens is a rare Creature — Siren card from Commander 2014 (C14), collector number 14. Current market price: $0.60, TCGplayer market prices via Scryfall.
{U}, {T}: Target creature attacks target opponent this turn if able. Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)