Dark Nova

Necrotic energy explodes in a 60-foot radius centered on a point you choose within range. Each creature in that light must make a Constitution saving throw. On a failed save, a creature takes 12d6 necrotic damage, and a dark sickness is inflicted on the creature. This creature has disadvantage on death saving throws and gains no benefits from rest, healing spells, potions, or other regenerative effects, such as Second Wind. A creature can repeat the saving throw at the end of each of its turns. On a success, the effect ends for this creature.