Path of Madness

You are filled with a 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 expected and insured violence.  When Raging, you become filled with glee, delighting in the pain of yourself and your enemies.  For some, it's the only controlled outlet of their psychotic and destructive tendencies, though control may seem like the last word you'd use to describe them.  Others take full revelry in spilling blood, and their Rage is just the extension of that.  Still more suffer from a curse of violence, or don't know or care about the why.  Whatever the cause,  this gives them enhanced abilities to live through the chaos of combat, leaving a trail bodies in their wake.  

Cheshire Grin

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 without 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 can’t speak or cast spells for 1 minute, and they lose concentration on active spells as their face contorts and twists into a cruel smile. At the end of each of its turns, the target can make another Wisdom saving throw. On a success, the effect ends.

Psychotic Step

At 6th level, you learn to journey through terrible shadow, though it fills you with a 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.

Aura of Violence

Starting at 10th level, your unique perspective grants you control over the scope and scale of things.  You gain immunity to the charmed and frightened conditions, and proficiency in Intimidation (or expertise if you are already proficient).  When you begin your Rage, you can cast enlarge/reduce on yourself, which doesn't require concentration when cast this way. The duration ends your CHA modifier turns after your Rage does.  You can also cast this once per CHA modifier (min 1) outside of your rage, and starting your rage doesn't end concentration on it.  CHA is your spellcasting modifier for these spells.

Bringer of Bloodlust

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 a 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.