Blood to bone.

Using accursed knowledge of bodies both living and dead. You use pure necromantic energy to turn a target blood to bone, and bone to blood. You target one creature of which you have a bone type. (Ie humanoid bone or humanoids, beast bones for beast, etc etc.) As you chant the incantation and pour the vial of blood over the bone your target must make a Constitution saving through against your spell save Dc. On a failed save the blood in their veins instantly turns to bone, and their bones instantly turn to blood. The target suffers 2d10 Necrotic damage and is paralyzed for the duration. On a successful save the target takes half damage and is not paralyzed. a Target that succeeds its saving throw can not be the target of this spell again for 24 hours. 

When cast using a spell slot of 2nd level or higher you may target 1 additional creature.