Vow of Malice is a uncommon Enchantment — Aura card from The List (PLST), collector number CM2-82. Current market price: $0.67, TCGplayer market prices via Scryfall.
Enchant creature Enchanted creature gets +2/+2, has intimidate, and can't attack you or planeswalkers you control. (A creature with intimidate can't be blocked except by artifact creatures and/or creatures that share a color with it.)