Breath of Vecna

You open your mouth wide as thick black haze rolls out forward across the ground in front of you in a 15ft. cone. All creatures within the haze must make a Constitution saving throw or suffer 1d4 necrotic damage. The haze weakens a creatures life force, making them susceptible to any necrotic energies which would attack the creatures life force. Any creature who failed the Constitution saving throw gains the Necrosis condition.

Until the end of your next turn whenever a creature affected by Necrosis would take necrotic damage, they take an additional amount equal to the damage of this cantrip.

This spells damage increases when you reach 5th level (2d4), 11th level (3d4), and 17th level (4d4).