Plunge into Darkness is a rare Instant card from Fifth Dawn (5DN), collector number 57. Current market price: $19.72 (foil $88.60), TCGplayer market prices via Scryfall.
Choose one — • Sacrifice any number of creatures. You gain 3 life for each creature sacrificed this way. • Pay any amount of life, then look at that many cards from the top of your library. Put one of those cards into your hand and exile the rest. Entwine {B} (Choose both if you pay the entwine cost.)