Demon harbinger

When you were young to prevent one from casing chaos a demon was sealed inside of you which works but it's effects come to the surface now and again when you feel deep emotion allowing the demons power run wild through you now it's up to you to decide if you want to control it or let it run wild.

Hellish resistance/Fearmonger

When you take this class at third level whenever you rage you gain resistance to fire damage

Also at third level whenever you make an intimidation check you may add you constitution modifier a well 

Demonic shift

Whenever you rage you can decide to use 2 rages to swap places with your demon and have him fight for you. ( This rage is considered as if you casted the summon greater demon spell) allowing you to choose a demon of challenge rating 5 (This increases to 6 at 10th level and 8 at 14th) This is considered a spell so it is affected by abilities such as dispel magic and counter spell and is considered concentration)only lasts until your rage ends.

Demonic resistance

Whenever a creature casts a spell that requires you to make a saving throw you have advantage on that saving throw

Greater demonic form

Whenever you have to make a con save on your demonic shift you may do so with advantage.