You touch a creature and cause them to wither into nothingness. That creature must succeed a constitution saving throw or be affected by a curse of withering. At the start of the target's turns for the duration, the target takes 1d6 necrotic damage and has their constitution score reduced by half the roll. A creature can repeat the save at the end of each of its turns, ending the effect on a success. 

If this spell reduces a creature's constitution score to 0, they die and wither to dust. Otherwise, the reduction lasts for the duration.