Path of the Runescar

This path combines the explosive fury of a barbarian with the destructive power of a spellcaster. The first runescarred barbarians were gladiator slaves who yearned for freedom. They created intricate rituals and mystic rites to infuse themselves with magical abilities. The barbarians who took this path used their abilities to escape confinement and have passed down the knowledge of how to take the path of a runescar to those they have deemed worthy. In a fight, runescarred barbarians can maintain magical effects while raging and make use of mystical abilities and utilize the hardiness of their bodies as a focus for their spells.

Runeskin

When you reach 3rd level, you augment your martial prowess with the ability to cast spells. See Spells Rules for the general rules of spellcasting and the Spells Listing for the sorcerer spell list.

Cantrips

You learn two cantrips of your choice from the sorcerer spell list. You learn an additional sorcerer cantrip of your choice at 10th level. You use your Constitution as your spellcasting modifier for these spells.

Cast the Runes

Starting at 3rd level, you can ignore the limitation on concentrating on spells while raging, but have disadvantage on concentration checks while raging. You can also use the runes etched into your skin as a spellcasting focus.

Runeskin

Choose three 1st-level evocation or transmutation spells from the sorcerer spell list. You can choose two additional 2nd-level evocation or transmutation spells from the sorcerer spell list when you reach 6th level and one additional 3rd-level evocation or transmutation from the sorcerer spell list at 10th level. You use your Constitution as your spellcasting modifier for these spells. The mystic words, symbols, pictograms, etc. of the spells are etched into your very skin. You can only cast the chosen spells while raging and only targeting yourself. You can cast these spells at a level equal to half your barbarian level, minus 2, rounded down (minimum of the spell's level). I.e., at barbarian level 12, you could cast a fireball spell at 4th level targeting yourself. You can ignore any somatic or material components of these spells, unless the material components have a monetary value assigned to them. You can change these chosen spells by performing a ritual over the course of 1 hour, which can be done during a short rest, to replace the etched spells with new etchings. The spells must follow the previously described limitations. While completing this ritual you must take no other actions until it is complete. If you are interrupted while completing this ritual, you lose the ability to cast the spells granted by this feature until the ritual can be finished. 

Runic Defense

Beginning at 6th level, if you would take acid, cold, fire, lightning, force, psychic, poison or thunder damage, you can use a reaction to become resistant to the triggering damage type until the start of your next turn. Also, the first time you hit with a melee attack on your next turn, the target takes an extra 2d6 damage of the triggering type. This damage increases by 1d6 at 10th level (3d6) and at 14th level (4d6). You can use this effect a number of times equal to your proficiency bonus and regain any uses at the end of a long rest.

Fortified Mind

Beginning at 10th level, when you are subjected to a Wisdom, Charisma, or Intelligence saving throw, you can add your Constitution modifier to the roll as a reaction. You can use this feature a number of times a day equal to your proficiency modifier and regain all uses on a long rest. Additionally, you no longer have disadvantage on concentration checks while raging.

Runic Branding

Once a day while raging, starting at 14th level, when you hit a creature with a melee weapon attack, you can choose to brand the creature with one of the spells chosen with the Runeskin feature. Until the end of your next turn, you cannot cast the spell, but any time the branded creature is hit with an attack, the spell is casted at the creature's location.