Grievous Wound is a rare Enchantment — Aura card from Duskmourn: House of Horror Promos (PDSK), collector number 102p. Current market price: $0.85 (foil $1.15), TCGplayer market prices via Scryfall.
Enchant player Enchanted player can't gain life. Whenever enchanted player is dealt damage, they lose half their life, rounded up.