Barbarians on the Path of the Rotten are more forces of nature than warriors.  They revel in entropy and decay, and their Rage taps into the Shadowfell to remind foes why death is something to be afraid of.

Reaper's Image

When you begin following this Path at Level 3, your Rage transforms you into a monstrous, decomposing visage of the undead that grants you the following features:

Rot Resistance: You resist Necrotic and Poison damage

Putrefaction Reaction: Your Unarmed Strikes now do Necrotic damage.  When you have less than half your maximum HP, they will also heal you for the same amount of damage plus your Barbarian level.  This secondary effect ends when you are no longer below half-health

Shake the Dead

At 6th level, the magic of the Shadowfell allows you to directly manipulate the dead.  As a magic action, you can place your hand on a corpse and perform a 10 minute ritual that will have the effect of either Animate Dead or Speak with Dead; you choose which when you begin the ritual.  You can use this feature a number of times equal to your Wisdom modifier (minimum of 1) per Short Rest

Brain Rot

At level 10, your mind has begun to fester, making it difficult to control or damage you through magical means.  Any attempt to read your mind automatically fails, you become immune to Psychic Damage, and you gain advantage on Int and Wis saving throws against spells.

Essence of Putrescence

At 14th level, your connection to the Shadowfell is complete.  You become immune to Necrotic and Poison damage while raging.  In addition your Rage generates an aura of necrotic energy 10 ft in all directions.  Any creature that starts or ends their turn in this emanation must make a Constitution save equal to 8 + Your Constitution Modifier + Your Proficiency Bonus.  On a failed save, they take 2d12 Necrotic Damage and only half on a success.  Plants automatically fail this save, while Constructs made of inorganic materials like metal are immune.