Silver ring in the shape of a skull with it's mouth open, your finger rests in between the jaws. 

Dormant:

User has +1 to spell attack bonus and spell save DC.

Enthralling Grasp: Once per day when you kill a non-undead humanoid creature in any way you may use a bonus action to raise their corpse from the dead as a Ghoul. You can use a bonus action is subsequent turns to issue verbal commands to this creature. Upon a long rest you may choose to use this feature to maintain control of the Ghoul or the ghast crumbles into dust. This use does count as your use of this feature.

Awakened:

User has +2 to spell attack bonus and spell save DC.

You gain resistance to necrotic damage

Touch of Undeath: When an undead under your control hits a creature with a melee attack they deal an additional 1d6 necrotic damage

Exalted:

User has +3 to spell attack bonus and spell save DC.

You gain immunity to necrotic damage.

When you use the Enthralling Grasp feature the creature raises as a Ghast instead. Also, you can use the feature twice each long rest.

Your Touch of Undeath feature now does 2d6 necrotic damage. 

You are now considered Undead as well as your other racial tags.

Notes: Bonus: Spell Attacks, Bonus: Spell Save DC, Enthralling Grasp, spellcaster that has made a pact with an Archdevil. When you attune the skull bites down on your finger holding it in place and binding you to your new master.