Vengeance demon hunters empowers themselves through the energies within, they are hunters that continue to be able to stand and fight when all else fails. By empowering themselves they are to take an enormous amount of hits and still come out victorious by the fights end.

Bonus Proficiency

Starting when you choose this mark at 3rd level, you gain proficiency in the Intimidation skill if you don't already have it. Your proficiency bonus is doubled for any ability check you make that uses this proficiency.

Torment

At 3rd level, you gain the ability to torment a creature. You can use your action and choose one creature that you can see within 30 feet of you. The target must succeed on a Wisdom saving throw against your fel save DC or have disadvantage on attack rolls against creatures other than you for 1 minute. At the end of each of its turns, the target can make another saving throw, ending the effect on a success.

Torment ends early on the target if you use this ability on a different creature.

Demon Spikes

Beginning at 6th level, your demon form is empowered by your demon mark, giving you resistance to bludgeoning, piercing, and slashing damage while in metamorphosis. Also while in metamorphosis, you have advantage on Strength and Dexterity checks and saving throws.

Immolation Aura

Upon reaching 10th level, you can spend 2 fel points as a bonus action to wreathe your body in flames of fel. When you activate this aura, and at the beginning of each of your turns for its duration, you take 1d6 fire damage. Immolation aura lasts for 1 minute, until you end it as a bonus action, or until you are knocked unconscious.

Whenever a creature hits you with a melee attack for the duration of immolation aura, you deal fire damage to that creature equal to 1d6 + half your Demon Hunter level.

Last Resort

At 17th level, you are able to draw life from your demon mark to escape death. When you are reduced to 0 hit points, you can expend 1 fel point (no action required) to have 1 hit point instead and enter your metamorphosis until the end of your next turn.