The Missing Link

You are a revered abnormality of the highest order. Some dragonkin of your clan may give you praise as someone whos' soul has been touched by Bahamut himself and be feared as a bane to other clans. Your appearance is more akin to dragons, but not so much so you are no longer considered of the dragonkin. Unfortunately, you still don't get the gift of flight...

Your likeness to dragons yields benefits:

• Feral Rage - blood of your ancestry is making itself known within you. As it boils, you drop your weapons and feel a powerful surge of strength within you (You now have the ability to use a variant of Rage of the Barbarian class. You can't use weapons in this state. You get all the benefits of Rage and also get +2 AC, -2 to WIS saving throws and +2 to Intimidation. Your unarmed strikes now deal a d6 + your strength modifier damage. In this state, you can be considered a mount, your walking speed is now double. In this state, you are able to scale walls and ceilings, your climbing speed is equal to your base walking speed. You can be mounted by creatures smaller than or of your size. If a creature tries to mount you, it has to roll Animal Handling check with -3. When mounted, creature has to roll Athletics or Acrobatics check with -3, if the roll is greater or equal to 14, the creature stays mounted. On failure, creature falls to the ground prone. On critical failure, creature is also incapacitated. On critical success, creature that is mounted no longer gets the penalty to the checks to stay mounted. If a creature has a feat to quell your anger, that creature doesn't get any penalties, while interacting with you. If someone has the Riding feat, they are allowed to mount and stay mounted on you without any rolls. If you are a Barbarian class, your Rage is replaced by Feral Rage)
• Dragons Breath - you feel a power stirring in your chest. You believe that you can breathe elements! (You gain an Ability to use a Breath Weapon. Now you can breathe in a cone of 20ft, but instead of 2d6 for damage you roll 2d4 + your strength modifier. If you originally didn't have a Breath Weapon and if you didn't have an affinity for a certain element, default Breath Weapon is poison)
• Dragons Roar - as you feel the surge of power, you can't help yourself but to let out your battlecry (As you activate your Feral Rage, opponents within 30ft of you have to roll a WIS saving throw. If the result is less than 14, they get frightened until your next turn. On critical failure, they are stunned instead) 
• Longevity - you have an abnormally long life, that can last centuries

However, while your blood boils, your rage festers:

• A Beast No Longer - while you were leaving destruction in your wake, someone has thwacked you on the head hard enough to make you reconsider your actions (If you become bloodied when Feral Rage is active, you have make a WIS saving throw. If the result is greater than or equal to 14, you become incapacitated until your next round. On failure, you are stunned instead. On critical failure, you are paralized. On critical success, instead of feeling drained, you feel that you can continue the assault, while mustering all the power of your fleeting rage, you get a point inspiration. After being bloodied, you can't reactivate your Feral Rage before you heal up to full)
• Bloody Frenzy - you are seeing red. Your brain is struggling to discern a friend from foe, while your heart desires to rip and tear, until you are bathed in blood (If there is at least an ally adjacent to an enemy when Feral Rage is active, make a WIS saving throw. If the result is greater than 10, you attack the enemy. On failure, you have to attack an ally. If there is a creature mounted on you, as a bonus action they can steer you towards the desired target, either giving you +2 or -2 on your WIS saving throw, or use an action to make you attack the desired target)
• Out of Breath - it is nice that you let out your battlecry, but it's quite awkward, when you can't do anything after it, isn't it? (When you activate your Feral Rage, make a STR saving throw. If the result is less than 14, you fail the check and are incapacitated until your next turn. On critical failure, you are stunned instead)