Enigmatic Companion

3rd level Possessed ability
Your companion spirit whispers from within, sharing obscure knowledge. You gain proficiency in Arcana, History, or Religion. You can replace this proficiency with another from this list as part of a long rest.

In addition, you can no longer be possessed by others.

Otherworldly rage

3rd level Possessed ability
When you rage, the spectral spirit of your companion manifests over you. The companion spirit is intangible and cannot be harmed.

When you rage, and as a bonus action on your turns for the duration, you can have the companion drain the life from a creature of your choice within 10ft of you.

A creature targeted by the companion must make a Wisdom saving throw (DC = 8 + your CON + your PB) or take 1d6 + PB Necrotic damage and be Frightened until the end of your next turn.

Grave promises

6th level Possessed ability
Your companion grows stronger as your lifeforce fades. While you are below half your maximum hit points, the damage from your companion increases by 1d6. This increases by an additional 1d6 when you reach 9th and 13th level in this class.

Ephemeral forms

10th level Possessed ability
You learn find familiar, and you can cast it as a ritual. When you cast it, your companion takes the form of the spirit you summon. The familiar's creature type is Undead, instead of its original.

In addition, the familiar can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object. The familiar vanishes while you rage.

Call of the Veil

14th level Possessed ability
When you use your bonus action to rage, your companion lets out a deathly wail. Each creature of your choice within 30ft of you must make a Wisdom saving throw (DC = 8 + your CON + your PB) or take 4d6 + PB Necrotic damage.

Your companion also lets out this deathly wail when you are reduced to 0 hit points by a hostile creature, though only once per long rest.

Possessed by Lucifer

Art by Bone dust