Breath of Decay

You conjure up the essence of a death god, exhaling their fetid breath onto your enemies to decay their life force. You exhale a deadly wind into a 15 foot cone. Each creature in that cone must make a constitution saving throw. On a failure, they take 3d10 necrotic damage and start decaying at the start of their turns. This decay deals 3d4 necrotic damage at the start of the creature's turn. At the end of a creature's turn, they can make another constitution saving throw to get rid of the effects. On a successful initial save, the target takes half damage and does not start taking damage at the start of their turns.

At Higher levels: For each spell level above 3rd that this spell is cast, the over time damage increases by 1d4.