Usable once per long rest, you allow Abbadon to take control. 
Aura of Entropy automatically activates, And sickening energy radiates out from you in a sphere with a 30-foot radius. While the spell lasts, the sphere remains centered on you and moves with you. Each hostile creature in the sphere has disadvantage on saving throws against becoming frightened, paralyzed,
poisoned, or stunned. Creatures in the sphere can't gain temporary hit points, and any effect that restores hit points to a creature within the sphere has those hit points
reduced by an amount equal to your spellcasting
ability modifier (minimum of 1). While you can do physical attacks in this form, your only castable spell becomes Entropy. 

You create a point of entropy in your hand and touch it to a creature or object
within range. Make a melee spell attack against the target. On a hit, the target
takes 1d8 force damage. This spell deals maximum damage if the target is an
object or is a creature that is grappled, incapacitated, prone, or restrained.

This lasts an hour, or until you succeed on a wisdom saving throw (DC 15).