Oath of Doom

You chose the doom as your oath 

Channel Divinity

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

Disruptive  Weapon. As an bonus action, you can imbue one weapon that you are holding with positive energy, using your Channel Divinity. For 1 minute, you add your Charisma modifier to attack rolls made with that weapon (with a minimum bonus of +1). The weapon also emits bright light in a 20-foot radius and dim light 20 feet beyond that. If the weapon is not already magical, it becomes magical for the duration.

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.

Back to hell - as an reaction when you reach zero hit points you cast a fireball on yourself that doesn’t damage you or fail any death saves the level of the fireball equals your proficiency bonus with a minimum of 3rd.

Oath Spells

You gain oath spells at the paladin levels listed.

Oath of Doom Spells

Aura of bane

Starting at 7th level,While you are conscious, hostile creatures within 10 ft. Subtract an d4 from all attacks and saves

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

Divine luck

Whenever you roll a 1 on a divine smite you can reroll the die and go with that number you can do this once per turn

Unholy transformation

At 20th level, as an action, 

you turn a creature into another kind of creature, the new form can only be an fiend whose challenge rating is equal to or less than the target's (or its level, if the target doesn't have a challenge rating). The target's game statistics, including mental ability scores, are replaced by the statistics of the new form. It retains its alignment and personality.

The target assumes the hit points of its new form, and when it reverts to its normal form, the creature returns to the number of hit points it had before it transformed. If it reverts as a result of dropping to 0 hit points, any excess damage carries over to its normal form. As long as the excess damage doesn't reduce the creature's normal form to 0 hit points, it isn't knocked unconscious.

The creature is limited in the actions it can perform by the nature of its new form, and it can't speak, cast spells, or take any other action that requires hands or speech, unless its new form is capable of such actions.

The target's gear melds into the new form. The creature can't activate, use, wield, or otherwise benefit from any of its equipment.