You touch a creature and cause them to wither into nothingness. That creature must succeed a constitution saving throw or be effected by a curse of withering. The target takes 1d6 constitution damage and have their constitution score reduced by half the damage they take at the start of each of their turns. 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.