Path of the Abomination

Whether through experimentation, intervention or ancestry, the primal rage within you has become so profound it has manifest into a dark and menacing entity.
Lurking in the corner of your conciousness, the Abomination surfaces during moments of extreme stress; taking xontrol of your mind and twisting your body into a monstrous form. For most, the Abomination is a thing to be feared, a thing that if not suppressed, controlled, or destroyed, will one day take permanent hold and wreak unspeakable havoc upon the world.

The Abomination

Starting at 3rd level, whenever you enter a rage, your body warps and your mind festers as the malevolent force within takes control - the Abomination. You may determine the Abomination's appearance.

When you enter a rage, you may swap a Mental score with your strength score until your rage ends.

Unstable Rage

Finally at 3rd level, the Abomination's fury spirals out of control as it grows threatened. When you enter a rage, and at the start of each of your turns while in a rage, roll a d20. If you roll a number equal to or less than your proficiency bonus, you then roll on the Unstable Rage table and apply the listed effect. The effect lasts until your rage ends (unless otherwise specified), and you cannot willingly end your rage on a turn in which you rolled on the table. 

Brokered Assistance

At 6th level, you gain proficiency in a Mental saving throw. In addition, you and you Abomination have learnt to work together towards shared goals. While not in a rage, you may give yourself advantage on any Strength check or saving throw. While in a rage, you can give yourself advantage on any check or saving throw using that mental stat. You may use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

Unstoppable

From 10th level, you can use your supernatural strength to fight off anything that stands in your way. When you would fail a saving throw while in a rage, you may use your reaction to repeat the throw, and use your Strength save modifier in place of any other ability save modifier. Once you use this feature, you can't use it again until your rage ends.

Repressed Genius

Starting from 14th level, your chosen mental score maximum is increased to 24. In addition, when your Strength score would be permanently increased, you may choose to increase your mental score instead.

Complete Control

Also from 14th level, before you would make a death saving throw on your turn, you may instead choose to trigger option 99-100 on the Unstable Rage table. If you do, you regain 1 hit point, roll half of your remaining hit dice, gain temporary hit points equal to the total, and stand up if you're prone. When you use this feature, you may enter a rage and take your turn as normal (if you have any rages remaining) otherwise your turn ends. You cannot use this feature while you are already under the effects of the 99-100 option of the Unstable Rage table.

Bonus proficenies

Gain proficiency in one skill and one musical instrument or Artisan tools of choices