Path of the Nordic Warrior

Vikings were raiders, mainly Norse or Hyberno-Norse, though also, sometimes, English. As such their main objective was to avoid battle whenever possible. In early years they would often be just one shipload of men, later a small fleet of ships. It was not until much later that they had large fleets of ships and actual armies. With a large fleet they would often land their fighting men at one spot, steal horses, and then raid across land to a meeting place that the fleet had now sailed to and there they would load the loot and send it off to places such as Normandy or Ireland to be sold. The raiders would then burn across another part of the country they were raiding and repeat the process until the raiding season was over and the crews were needed back home for harvest and then winter over in comfort.

Mjölnir's Blessing

When you choose this path at level 3, you gain the ability to call forth the storm from within.
Mjölnir's Blessing. The first time you make a melee attack on your turn, you can choose to add 1d8 lightning damage to your attack. This feature has a number of charges equal to your wisdom modifier, starting at 0. Every time you use this feature it adds a charge Mjölnir's Blessing.

Overcharge. When you accumulate the maximum amount of charges, your body is struck by pure energy from within your runic self, damaging yourself for 1d8 lightning damage. Once you recieve this damage, your charges of Mjölnir's Blessing reset back to 0. 

Runic Frenzy

Starting when you choose this path at 3rd level, you can go into a frenzy when you rage. If you do so, for the duration of your rage you can make a single melee weapon attack as a bonus action on each of your turns after this one. You suffer no exhaustion from this frenzy. 

Bearer of the Lightning

When you reach 6th level, you gain the ability to control the lightning you summon. During your rage you can cast the spell: "lightning bolt". The following conditions apply to your spell casting. 

• You must be raging before casting of this spell. 
• Wisdom is you spell casting modifier for this spell. 
• You may cast this spell a number of times equal to half the number of rages you have rounded down to a maximum of 4 for every long rest.

Vessel of Hríð

The Vessel of storms. Starting at 10th level you gain the ability to cast the "Call lightning" spell during your rage. The following conditions apply to your spellcasting.

• You must be raging before casting and mantain that rage throughout the duration of the spell.
• Wisdom is you spell casting modifier for this spell. 
• You may cast this spell twice for every long rest.
• Concentration applies as if you were a regular caster. 

Lightning Caller. Additionally your superb control over lightning has given you resistance to the power you control, you gain resistance to lightning damage. 

Stormviðri Herald

Starting at the 14th level, your frightening presence cannot be ignored by the gods any longer, when you rage, an aura spanning a 10 ft. circle, centered around you, surrounds your body and surroundings, the aura has the following effects.

• Storm Ruler. Starting after you rage, if an enemy starts their turn inside your aura, they are struck by random chains of lightning, receiving 1d6 lightning damage.
  Nordic Presence. Any ally that starts their turn in combat inside your aura has advantage on all attack rolls to any enemy that ended is placed within the same aura. You yourself cannot benefit from the advantage given by Nordic Presence.

Descendant of the Víkingr

When you reach level 14 in this subclass, you unlock the full power of your Viking bloodline, whenever you kill an enemy while wielding a Shield and one of the following weapon types: 

• Long Sword
  
• Battle Axe
  
• War Hammer
  

You can choose to use your reaction to make a Battle Cry gaining temporary Hit Points equal to your Barbarian Level + Your Constitution Modifier,  additionally, forcing a creature within the aura granted by your Nordic Presence feature to make a wisdon saving throw or be frightened by you until the end of your next turn. 
The DC for said saving throw is equal to:

• 8 + Wisdom Modifier + Proficiency Bonus