Barbarian, Path of the Parasite

Barbarians who walk the Path of the Parasite harbor an intimate connection with an age-old parasitic entity thriving within their very being. This creature feeds on the barbarian's flesh, exchanging sustenance for raw might during moments of fury, bolstering their offensive prowess to fearsome heights.

Nurtured by a curious rapport, the parasite's existence becomes inextricably intertwined with the barbarian's essence. Over time, the consuming partnership gradually tilts in favor of mutual benefit. The tenacious barbarians who ascend to greater tiers of power achieve a remarkable equilibrium with the parasitic lifeform, evolving their dynamic into a harmonious symbiosis that enhances their capabilities in ways that far outweigh the initial cost.

Flesh Burner

Starting when you choose this path at 3rd level, your parasite instinctively consumes your lifeforce in exchange for giving you more power in battle. When you enter your rage, you can choose to activate Flesh Burner, draining hit points equal to your constitution modifier at the end of each of your turn. The amount of hit points drained from Flesh Burner cannot be reduced by any means. While Flesh Burner active, you gain the following benefits:

• you gain bonus to max hit points equal to twice your proficiency bonus + 2 for each level you have on this class.
• bludgeoning, piercing, and slashing damage that you take from attacks is reduced equal to your rage damage.
• your attacks deal an additional damage equal to half your constitution modifier (rounded up).

For the duration of your rage, you can toggle this feature on and off as a bonus action at the start of each of your turn after this one.

Parasitic Extraction

Beginning at 6th level, you can infuse your attacks with flesh-eating parasites that burrows into the body of your foes. When you hit a creature with a melee weapon attack, you can choose to activate Parasitic Extraction. The target must make a Constitution saving throw with the DC of 8 + your Constitution modifier + your proficiency bonus or take 1d4 piercing damage and have a parasite burrows into them. For the duration of your rage, creature that has your parasite takes necrotic damage equal to 1d4 + your proficiency bonus at the start of each of its turn, the necrotic damage bypasses resistance.

Creature can repeat the saving throw at the end of each of its turn, forcing the parasite to exit in a successful save. The parasite exits in a space within 5 feet of the creature and it has a stat-block. As a bonus action, you can grab and invite the parasite back to your body while within 5 feet of it. The parasite fuses back to your flesh and you regain a number of hit points equal to the damage dealt by the parasite. In addition, you can instead choose to grab and throw the parasite as a bonus action to an allied creature within 30 feet of you and heal them equal to the damage dealt by the parasite.

You can use this feature a number of times equal to your Constitution modifier (minimum of once), and you regain all expended uses after finishing a long rest. When you reach certain levels in this class, the amount of damage from your Parasitic Extraction feature increases: by 1d6 at 6th level, by 1d8 at 10th level and by 1d10 at 14th level.

Mass Monster

At 10th level, your parasite learned to resist illness and take off chunks of flesh from deceased foes, adding their mass to yourself and further protect your body from harm. You gain advantage on saving throws against disease and poison. In addition, whenever you kill or reduce a creature to 0 hit points, you gain temporary hit points equal to 1d4 + the slain creature's constitution modifier.

Symbiosis

At 14th level, the parasite's body, mind and soul fused with you, attaining perfect symbiosis and you both now living as a single entity. When you roll a Hit Die to regain hit points, the minimum number of hit points you regain from the roll equals 3 + your Constitution modifier. In addition, you can choose the body of a deceased large or smaller creature within 5 feet of you and devour it as an action. You regain hit points equal to 5 + the creature's hit die, gain 1 use of Parasitic Extraction and your next attack deals additional damage equal to the devoured creature's hit die.

You can use this feature a number of times equal to half of your proficiency bonus (rounded down) and you regain all expended uses when you finish a long rest.