Death Armor

Source: Forgotten Realms - Heroes of Faerun

Level 2 Necromancy (Sorcerer, Wizard)
Casting Time: Action
Range: Touch
Components: V, S, M (an onyx worth 50+ GP, which the spell consumes)
Duration: 1 hour

For the duration, an inky aura surrounds one creature you touch. The target has Advantage on Death Saving Throws, and once per turn, when a creature within 5 feet of the target hits it with a melee attack roll, the attacker takes 2d4 Necrotic damage.