You launch a vaguely crossbow bolt shaped projectile from your hands. More specifically, the bolt is black and the head is vaguely shaped like a skull. Make a ranged spell attack against the target. On a hit, the target takes 1d6 necrotic damage and has to make a constitution saving throw (vs your spell modifier). On a failed save, they take an additional 1d4 necrotic damage after their turn for the next five rounds. The duration of the effect effect increases by five rounds when you reach 6th level, 12th level, and 18th level.