Lys Alana Scarblade is a uncommon Creature — Elf Assassin card from Lorwyn (LRW), collector number 122. Current market price: $0.36 (foil $3.29), TCGplayer market prices via Scryfall.
{T}, Discard an Elf card: Target creature gets -X/-X until end of turn, where X is the number of Elves you control.