Escalating Rot

A surge of repulsive black energy streaks towards a target creature you can see within 90ft. The creature must make a Constitution saving throw against your spell save DC, taking 12d10 necrotic damage on a fail, or half as much on a success, as the energy causes its flesh and bones to rot and wither. Additionally, on a fail, the affected creature has vulnerability to all damage and takes 3d4+5X necrotic damage at the end of each of their turns where X is the number of turns they have been under the effects of Escalating Rot. Afflicted creatures can repeat this saving throw at the beginning of each of their turns, and the effect can be removed by a Greater Restoration spell or a Remove Curse spell. For every minute a creature is affected by this spell, they gain a level of exhaustion.