Capture Soul

You surround a creature in range with a foreboding force that threatens to steal its soul. If the creature is killed within the duration, it must make a Wisdom saving throw against your spell save DC. A creature automatically succeeds this saving throw it it has an intelligence of less than 5, or doesn't have a soul; this includes constructs, certain types of undead, and other creatures subject to your DMs discretion. Any type of wraith, ghost, or other spectral form of undead that doesn't automatically succeed this save instead automatically fails this save.

On a failed save, you rip the soul from the creature upon its death, which is sealed in the container used as the material component for this spell. Although this item is inanimate, it represents the creature's literal soul, which cannot return to its body. If this soul is consumed or as long as it remains contained, the creature cannot be brought back to life. If the container is destroyed, the soul fades away, moving on to its respective afterlife. 

As an action, the trapped soul can be consumed, destroying the trapped soul and restoring 2d6 hitpoints to the creature who consumed it. This ability also imparts one random minor positive or negative effect on the creature that consumed the soul, dependant on what that souls alignment was in life. This is subject to the DMs discretion.