Oath of Death

The path that has lead you to becoming such a killing machine has not been easy. However in your ear you could always hear the whispers of an entity encouraging you to continue. When you listened to it, you felt powerful, when you didn't, you failed your goals. It may have started with beating the bullies at the playground, but it has ended with slaying the deserved. Eventually, potentially sacrificing some innocence to do so. Many Oath of Death Paladins choose this oath after dying and being resurrected. Having met with the god of death they believe has been encouraging them and accepting them as their deity. Or experiencing an eternal blissful sleep, just to be brought back into a world of pain, vowing to make sure those you kill dont experience the sorrow you feel now. The worst of them come from Undead Paladins. The Undead kind mostly end up losing themselves to the chill of death, becoming akin to that of a lich, unable to feel mortal emotions. (For the publics FYI, I know this is broken for a regular dnd campaign. I've designed this with my groups game in mind.)

Negative Energy Acceptance

Taking this path comes at a great cost. All Radiant damage spells and abilities that you learn instead deal Necrotic damage. In addition to this, all spell healing you receive is lowered by your level and you lose the ability to cast any healing spells. However, you gain Immunity to Necrotic damage and can heal for 1 free hit die when you would have been dealt necrotic damage.

Channel Divinity

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

Weapon of Desecration. As an action, you can imbue one weapon that you are holding with Negative energy, using your Channel Divinity. For 1 minute, you add your Charisma modifier to attack and damage rolls made with that weapon (with a minimum bonus of +1). You can also cast a spell through the weapon as a bonus action after taking the attack action. The spell can only be one in the extended spell list.

You can end this effect on your turn as part of any other action. If you are no longer holding or carrying this weapon, or if you fall unconscious, this effect ends.

Command the Unholy. As an action, you present your Unholy symbol and speak a Command towards fiends and undead, using your Channel Divinity. Each fiend or undead, 1/4 your level and lower, that can see or hear you within 30 feet of you must make a Wisdom saving throw. If the creature fails its saving throw, it is under your command for 1 minute. 

Creatures under your command will do their best to fulfill your requests. Attack, Movement, Guard, or Hold Position commands can be given as a bonus action on your turn. If no commands are given, the Creatures will attempt to hold their position and defend themselves the best they could.

Oath Spells

You gain oath spells at the paladin levels listed.

Oath of Death Spells

Aura of Death

Starting at 7th level, you and friendly creatures within 10 feet of you gain your Charisma Modifier to spell attacks and spell DC's and an equal amount in Necrotic damage. Also enemies with Necrotic immunity take necrotic damage as if they only had resistance.

At 18th level, the range of this aura increases to 30 feet.

Layer of Shadow

Beginning at 15th level, you are always under the effects of a Armor of Agathy spell. This spell scales with your level.

Angel of Death

At 20th level, as an action, you can transform into an angel of death. Your appearance transforms either to have flightless bone wings, or a body cloak of shadow or you lose your flesh and become a skeleton, etc. For 1 minute, you gain the ability to destroy your body and reform at a location where a corpse or a skeleton is located, reforming from the material of that dead creature.

You cast a shadow in a 60 foot radius, Enemy creatures that start their turn within your shadow must make a Constitution throw or take your level in necrotic damage.

In addition, for the duration, Weapon of Desecration and Command Undead are both active and you gain bonuses to them.

Weapon of Desecration becomes a Pure Black Shadow Scythe, able to hit any creature within 60 ft. Attacks deal your level in bonus damage and become pure necrotic damage that cannot be negated or reduced.

Command Undead can affect creatures 3/4 your level and lower. Creatures 1/2 your level and lower roll with disadvantage. Creatures 1/4 your level and lower automatically fail.

Once you use this feature, you can’t use it again until you finish a long rest.