Any spiked armor you have equipped is considered a simple melee weapon that deals your training die of piercing damage on a hit. Moreover, a creature grappled by you while you have a spiked armor equipped takes your training die of piercing damage at the start of its turn.
While raging, when you use your Reckless Attack feature, you gain temporary hit points equal to your twice your barbarian level.
While raging, when you take the Move action on your turn, you can take the Attack action using your Impaling Armor feature as part of the same action. On a hit, you ignore any Attack action taken as a reaction when you take the Move action from the target until the end of the turn.
While raging with a spiked armor equipped, any creature within 5 feet of you that attacks you with a melee attack takes two of your training die of piercing damage.
You can take the Attack action as two actions to target each creature within 5 feet of you with the spiked armor using your Impaling Armor feature. On a hit, a creature takes an additional four of your training die of piercing damage.
Once you use this feature, you can't use it again until the start of your next turn.