Path of the Undying

You seek worthy opponents, and a worthy death through battle. This near-religious fervor for carnage and fights makes you seek out those who would do harm to you. A type of warrior associated with the undying god called Gorroth.

Improved Relentlessness

Starting when you choose this path at 3rd level, you come back from death whenever you are raging- eager for more violence, you can no longer willingly exit out of rage. You gain the Relentless Rage feature (with adjustments):

If you drop to 0 hit points while you’re raging and don’t die outright, you must make a DC 10 Constitution saving throw. If you succeed, you drop to 1 hit point instead.

Each time you use this feature after the first, the DC increases by 5. When you finish a short or long rest, the DC resets to 10.

In addition, should you succeed the saving throw to drop to 1 hit point, you also gain temporary hitpoints equal to three times your barbarian level. If you would reach zero hitpoints and have passed this saving throw two times since your last short or long rest, you will die if you fail the saving throw. If you fail a saving throw and become unconscious before you reach the two success limit, you can no longer utilize this feature (your rage becomes normal) until you complete a long rest.

At level 11, when you normally would receive Relentless Rage, you will instead make these Constitution saving throws with advantage.

Savage Retaliation

Beginning at 6th level, while you are raging and have below your maximum hitpoints rounded up in health, you gain advantage on melee attack rolls. In addition, while in this low health state, you have advantage on Charisma saving throws if you have successfully rolled at least once for Improved Relentlessness.

Roar of a Slayer

Beginning at 10th level, you can use your action to roar a challenge to creatures of your choice within 60ft of you. If they can hear you, they must make a Charisma saving throw equal to 8+proficiency bonus+Charisma modifier. If you are below half your hitpoints rounded up then you may add your Strength modifier to the DC. On a failed save you may choose to have them have disadvantage on attacks against anyone other than you, or to have disadvantage on attacks against you. When you make this choice it applies for all creatures affected. On a successful save nothing happens.

You may use this feature a number of times equal to your proficiency bonus. All uses are regained on a long rest.

Fury of a Cornered Beast

Starting at 14th level, when you take damage from a creature that is within 5 feet of you, you can use your reaction to headbutt them. The creature must make a Constitution saving throw with a DC of 8+proficiency bonus+Constitution modifier. On a failed save they are stunned until the end of your next turn and take 2d6 bludgeoning damage. On a successful save they only take half the bludgeoning damage. If you are below half your hitpoints rounded up and have made at least one successful Improved Relentlessness saving throw, you may add your strength modifier to the DC.