Oath of Immortality

"By Black and White, By Red and Blue My Colors Shall Shine True
I Shall Be Free for Eternity, Hidden from Death
This is the Oath of Immortality."
                                                      - Kalabasher P. Dragonflare

 

The Oath of Immortality is Like an OathBreaker Becoming a Death Knight or a Wizard Becoming a Lich.

An Oath of Immortality Paladin Promises to Become a Soldier and Bringer of Death while Hiding From it Themself a True Reaper.

Channel Undeath

When you take this oath at 3rd level, you gain the following two Channel Divinity options.

Undead Aura: As an Action You can Shoot out an Aura for 50 ft. and Any Undead in That Area Follow Your Commands for 1 Hour, If the Creature(s) is Already under the Influence or Control of another Creature it must First Succeed a DC 8 + Your Proficiency Bonus Wisdom Saving Throw, If the Creature Fails the Save it Falls Under your Control, To take Control of Any Undead it Must have an Intelligence or Wisdom Score of 10 or Lower.

Death Touch: As a Bonus Action a Weapon you Wield becomes Enveloped in a Black Aura, For the Next Minute all Weapon Attack you make with it Against a Creature the Attack Deals an Additional 6d6 Necrotic Damage, If a Creature Dies from an Attack while this Active the Creature Rises as a Wight Under your Control.

Oath Spells

You gain oath spells at the paladin levels listed.

Oath of Immortality Spells

Timeless Being

When you Reach 7th Level, You have become Immune to the Effects of "Death", You are no Longer considered a Humanoid you are Now considered a Celestial and Undead, a Bi-Product of your Transformation is that you no Longer Need to Eat, Sleep, Drink or Breathe.

You also Gain the Ability to cast the Blight Without Spending a Pact or Spell Slot.

Touched by Death

Overtime Your Body has Become More and More Decayed and Gnarled and  Lesser Undead Creatures, Such as a Zombie or Skeleton, have Become Passive Towards Whether or Not They Were Told to Attack You.

Your Body has Also Become More Vulnerable and Brittle While in Battle You May Lose Body Parts if You Find Spare Skeletal or Rotting Parts can be Used to Replace old Parts but If You find a Part You Would not Normal You can Cast a Ritual to Combine them Into Your Body so You Can use Said Part.

As well as When you Are Effected by Necrotic Damage you instead Heal than take Damage, if You Heal over your Maximum Hit Points you gain Temporary Hit Points, 

Commander of the Undead Horde

Finally at 20th Level, You have Reached the Apex of an Undead Creature, an Undead Commander, As an Undead Commander all Creatures of the Undead Creature Type Have Disadvantage on all Rolls Against you.
Your Divine Smite Ability no Longer Deals Radiant Damage it Instead Deals Necrotic and Radiant Damage (If you have Access to Metamagic such as with the Metamagic Adept Feat It can be Affected by your Metamagic)
Whenever a Creature of the Undead Type Walks within 30 Feet of you it Must Make a DC 10 + your Spellcasting Modifier Wisdom Saving Throw or Be Forced under your control for 1 Hour.