Yenma's Sphere of Destruction

A 5ft diameter sphere of energy manifests from you. Target a creature within range (Must have a soul or an undead with a connection to the Negative Material plane or that is animated by negative energy.) The sphere will then moves 10ft at the end of each of your turns towards the target. 

If the sphere passes through a space occupied by a creature that creature must make a Dexterity saving throw against your spell save or take 20d8 as un-resistible damage. On a successful save the creature takes half damage.

The sphere passes through any object, construct, or creation of magical force (Such as the wall created by "Wall of Force") leaving behind a 5ft diameter hole.

The sphere will continue to follow the targeted creature until it hits the target, the target makes its save, or if the sphere is dispelled.

Once the sphere enters the space that is occupied by the target the target must make a Dexterity saving throw versus your spell save, on a failed save the target takes 20d8 as un-resistible damage. On a successful save the creature takes half damage.

Any creature whos Hit points is reduced to 0 by the damage of this spell, has their soul or any connection to the negative plane Destroyed.

This spell targets the target's soul (If it has one) meaning if the target is a lich and has its soul leave its body to its Phylactery before it is destroyed as long as the Phylactery is on the same plane as the Sphere it will continue to follow the targets soul all the way to its Phylactery.

Once casted, the caster looses (10 x their Spell casting ability modifier, minimum 10) hit points.