Path of the Undying

Death need not be the end of a barbarian's path. Sometimes, beyond the jaws of eternal rest, a new path of bloodshed lies. To return to the land of the living, consumed with hatred and prepared to engulf your foes with necrotic wrath; that is the might of the Undying Barbarian.

Revenant's Curse

When entering rage, you can make an enemy you see in a radius of 15 feet from you roll a wisdom saving throw. On a failed save, the creature is named your nemesis.

While your nemesis, the creature cannot cast spells and has disadvantage on attacks against you. When attacking your nemesis, you have advantage and deal an additional 2d8 necrotic damage, gaining another 1d8 of damage every feature level. (6th: 3d8, 10th: 4d8, 14th: 5d8)

When attacking another creature or slaying your nemesis, this feature ends. Once used, this feature cannot be used until the next long rest.

Might of the Dead

When entering rage, you become immune to necrotic damage and regenerate half as much hit points as total damage done from attacks. 

Aura of Necromancy

When entering rage, you can summon the claws of ghouls to sprout out of the ground around you in a radius of 20 feet.
Enemies in this radius have their movement speed halved and must roll for strength or be restrained by the claws. While restrained, they are unable to move and you have advantage on attacks against them.
Allies in this radius suffer no ill effects.

Undying Berserker

When your hit points reach 0 while in rage and you are not killed outright, you return to life at half of your maximum hit points and do double damage with melee attacks for the next 1d6 turns.