Nightmare Lash is a rare Artifact — Equipment card from Mirrodin (MRD), collector number 219. Current market price: $8.74 (foil $12.41), TCGplayer market prices via Scryfall.
Equipped creature gets +1/+1 for each Swamp you control. Equip—Pay 3 life. (Pay 3 life: Attach to target creature you control. Equip only as a sorcery.)