Path of the Ferrous BattleRager

A ferrous battlerager excels in grappling and causing damage to those in close quarters to them.  Additionally, while raging they harden their skin and become harder to deal damage to.  

A ferrous battlerager cannot gain this subclass by studying alone but some quirk of birth/fate/magic/technology must allow them to have the capabilities of skin-hardening.

Examples:

1. Someone of Dao descent could have a metallic body that internally heats up in a rage allowing pressure points to form spikes and the skin to become purer metal and harden.

2. A child of a wild magic sorcerer could spontaneously create spikes of any variety and tough elephant, dragon, or tarrasque skin while raging.

3. Someone could buy a modified alchemist created iron suit that activates during a rage.

Hardened Skin

While internal fires rage, your skin purifies and hardens making it harder for anything to pierce.

While raging, add your proficiency bonus to your AC.

Battlerager Armor

When you choose this path at 3rd level, you gain the ability to use spiked armor (see the “Spiked Armor” sidebar) as a weapon.

The internal pressure building up inside of you releases at pressure points you have chosen when working on your spiked armor.  The holes carefully placed allow you to grow spikes that you are able to most effectively use while raging.

Your unarmed strikes can deal bludgeoning or piercing damage equal to 1d6 + your Strength modifier on a hit. If you aren't wielding any weapons or a shield when you make the attack roll, the d6 becomes a d8.

While you are wearing spiked armor and are raging, you can use a bonus action to make one unarmed strike with your armor spikes against a target within 5 feet of you.  

Additionally, when you use the Attack action to grapple a creature, the target takes 1d6 damage if your grapple check succeeds, and 1d6 at the end of every one of it's turns that it is still grappled.  This damage becomes 2d6 at level 6, 3d6 at level 10, and 4d6 at level 14.

SPIKED ARMOR

Spiked armor is a rare type of medium armor made usually by dwarves. It usually consists of a leather coat and leggings covered with spikes that are usually made of metal.
Cost: 75 gp
AC: 14 + Dexterity modifier (max 2)
Weight: 45 lb.

Petal to the Metal

Beginning at 6th level...

You can bonus action dash while raging.  During this dash you may move through enemy squares, though if you would end in an enemies square, place yourself instead in an empty square within 5ft.  You must not be grappling or grappled in order to use this.

You may make an unarmed melee strike against every enemy you passed through.

Additionally, when you hit a creature with an unarmed strike or an improvised weapon on your turn, you can use a bonus action to attempt to grapple the target.  

Pinning Spikes

Beginning at 10th level, you can use an action to try and pin a creature grappled by you(must be done near ground or wall or object they can be pinned to).  To do so, make another grapple check.  If succesful, you shoot a spike through them into the surrounding environment succesfully restraining them.  You may leave the grapple and they will still be restrained until they can succeed on a strength check DC 8 + Str + Prof.  They can try to make that check at the end of their turn.

Spiked Retribution

Starting at 14th level, when a creature within 5 feet of you hits you with an attack you can use your reaction to hit them back.  The creature must make a Dex saving throw, it takes 4d10  damage on a failed save, or half as much on a succesful one.

If you are raging, the range is increased to 60 feet, as you shoot off spikes to pay them back.