Unkown Decision

You learn the powers wielded by the Undead against mortals and have found a way to protect yourself.  You sacrifice 3 lesser creatures and consume their essence in order to gain three affects when they come from Undead Creatures.  You also now produce a distinct necrotic aura that can be seen by Undead, Fiends, Celestials, and Fey creatures.

First you are immune from the Charmed, Frightened, and Possessed Conditions.

Second you have advantage an all saves from the Poisoned, Diseased, Stunned, Paralyzed, Blinded and Deafened Conditions.

Third if you die while under this spell you body, shadow or soul can't be turned into an Undead even if it would normally do so.  This does not prevent someone from casting Revivify or other such spells on you.