Path of the slow decay

Barbarians that follow the Path of slow decay are cursed from the very moment they are born, gifted with a terrible illness destined to kill them, with the only way of preventing the death being ending the life of others, someone afflicted with this disease becomes stronger, but it will slow both their physical and mental capabilities, reducing them to nothing more than a glorified meatshield. However, in rare circumstances, the mental decay acts slower in a victim's body, leading to the Path of the slow decay Barbarians, this tribe of mismatched races and histories is comprised of victims afflicted with the illness who are lucky enough to starve off the decay of their minds by using extensive training and the study of special techniques to help in keeping the infection at bay.

The Malaise

Because of the Malaise infecting your body, you are in a constant state of decay, causing your body to slowly rot and reduce your overall health over time.

Each time you take any action on your turn, take 1d10 damage, this damage cannot be reduced in any way.

Calming rage

When in rage, instead of dealing extra damage, you heal health equal to your rage modifier each time you hit a target with a melee weapon attack.

Tainted Blood

Starting at 6th level, the Malaise in your body reaches a dangerous level of toxicity, allowing you to use your own blood as a weapon, as a bonus action on each of your turns, you can deal 1d6 damage to yourself that cannot be reduced in any way, doing this allows you to deal an extra 1d8 poison damage with every melee attack you make for the rest of your turn.

Throat of the decayed

Your vocal cords have rotted away enough for them to become similar to that of Undead creatures, you can only communicate through grunts, moans, and growls, but can communicate clearly with any undead creature and vice versa.

Casting "Speak with dead" of you allows you to communicate normally for the spell's duration.

Decayed flesh

Due to your rotting flesh, you have become more resilient to poisons and Necrotic magic. 

You have immunity to Necrotic damage and have advantage on saving throws against the Poisoned condition.

Serenity

The greatest technique of the Slow Decay Barbarians, the Serenity meditation involves the warrior resting for a moments time and clearing their mind to focus on nothing at all, doing so somehow restores the warrior's body to restore its energy and be in fighting condition once again.

You can use an action on your turn to heal Xd12 health, where X= Your wisdom modifier + Your proficiency bonus.

You can use this feature a number of times equal to your Proficiency bonus and regain all uses after a short rest.

Avatar of decay

Your resilience to death itself has borne fruit, as you now have achieved the true power of the Malaise infecting you, allowing you to spread the illness to others with just your blood. 

You can use an attack action to deal 1d12 damage to yourself that cannot be reduced in any way, after this the next target you hit takes an extra 1d10 poison damage and then becomes your Effigy of decay, whenever your Effigy moves, takes damage, or deals damage, it takes 1d6 Poison damage that cannot be reduced in any way, you then recover 1d6 hit points