Aura of Decomposition (MM)

This cantrip creates an instant aura of decay around the caster in a 5' radius. All creatures in range must make a Constitution saving throw or take 1d4 points of necrotic damage and inflict half damage on their next successful weapon attack before the caster's next turn.  If the target saves, they take no damage and suffer no other effect.

At Higher Levels:  The cantrip does an additional 1d4 necrotic damage at 5th (2d4), 11th (3d4), and 17th (4d4) level.