Path of Mercurial

Your rage is not a rage at all. Instead you are filled with malicious spite that runs wild within your veins, bringing a cruel smile to your face and causing the shadows around you to writhe and twist in sympathy. Many who walk path find themselves in contact with the Shadowcat: an unusual creature that wanders the planes devouring nightmares, twisting fate, and causing mischief for some inscrutable end.

As you learn to walk the planes like it does the cruel joy within your heart grows ever stronger, granting you powers unseen by mortal men. You are the stalking panther, the hunting lion, and the sly grin that appears even as your form fades away. Become nightmare.

Cheshire Grin

When you choose this path at 3rd level, your rage forces a terrible smile upon your face. When you use your Reckless Attack feature while raging, shadows begin to writhe around your form until the start of your next turn. If you take damage from an attack during this time, you can use your reaction to move up to 10 feet with out provoking opportunity attacks and you become invisible to your attacker until the start of your next turn.

Whenever your rage ends, you can choose to inflict that same malicious grin upon another creature. Choose a creature within 30 feet that can see you. The target must make a wisdom saving throw (DC equal to 8 + your proficiency bonus + your Charisma Modifier). If they fail, they cant speak or cast spells for 1 minute, and they lose their concentration on active spells  as their face contorts and twists into a cruel smile. 

On the end of each of its turns the target can make another Wisdom saving through. On a success, the effect ends.

Down the Rabbit Hole

At 6th level, you learn to journey through terrible shadow, though it fills you with wicked madness. When you enter your rage, you can teleport up to 30 feet to an unoccupied location you can see, and while raging you can do so again whenever you reduce a creature to 0 hit points.

Looming Shadow

Starting at 10th level, your unique perspective grants you control over scope and scale of things. You can cast enlarge/reduce at will, even while raging. You can maintain concentration on this spell even while you are raging, and entering your rage does not cause you to lose concentration. Charisma is your spellcasting ability for this spell.

All that Remains

Starting at 14th level, when you use your reaction to activate your Cheshire Grin feature, you can choose to have your wicked smile hang in midair, fully visible. you still gain the benefits of invisibility against your attacker, but now each creature within 15 feet of you who can see your grin, including your attacker, must make a Wisdom saving throw against your Cheshire Grin save DC. If the creature fails, they are enraged by your taunting grin and must attack you with a weapon or spell attack before the end of their next turn or take psychic damage equal to your barbarian level. If their first attack misses they take half as much damage. Creatures immune to the Charmed condition are unaffected.