Path of Eternal Hunger

The Path of Eternal Hunger Barbarian is a dark, primal warrior cursed (or blessed) with an insatiable need for power, life force, and strength. This Barbarian thrives in the heat of battle, drawing life from fallen enemies and becoming stronger the more they fight. This subclass can be flavored as anything from a cursed soul to a warrior tapping into a forbidden, vampiric bloodline.

Devouring Strike

When you hit a creature with a melee weapon attack while raging, you can choose to deal an additional 1d4 necrotic damage. You then regain hit points equal to the necrotic damage dealt. This healing increases to 1d6 at 10th level and 1d8 at 15th level.
You can use this feature a number of times equal to your proficiency bonus, resetting after a long rest.

Predatory Instincts

 As a bonus action, you can detect all living creatures within 60 feet of you, even if they are hidden or invisible, for 1 minute. During this time, you have advantage on attack rolls against any creature within this range with less than half its hit points. You can use this feature a number of times equal to your proficiency bonus, regaining all uses after a long rest.

Life Siphon

While Raging, when a creature within 15ft of you regains hit points via a magical effect, spell, or potion, half of the hit points restored to that creature instead comes to you. If you are at maximum hit points, you gain temporary hit points up to a maximum of your Barbarian level. 

Death's Gluttony

If you reduce a creature to 0 hit points while raging, you gain advantage on all melee attacks until your rage ends for up to a minute.
Additionally, when you make a melee attack with advantage, any necrotic damage delt by the attack is doubled.