You point at a creature within range, and attempt to make it's skeleton rip free of it's body. The creature must make a Constitution saving throw. The target takes 7d10 + 7 necrotic damage on a failed save, or half as much damage on a successful one. If this damage kills the target creature, it's flesh sloughs of it's skeleton, collapsing a pile, and the skeleton becomes a Skeleton (Basic Rules, pg. 152), hostile to all living creatures that attacks the closest target.