Those who wander the wilds must make its dangers into their own weapons. Stormcloak rangers wield lightning and thunder to a mighty effect, whether they favor melee weapons or ranged. The first Stormcloak rangers were orcs, who relished the dread that their powers inspired and gained some protection from the wizardry of the elves; from the orcs it passed to their half-orc children, some of whom turned it to the nobler cause of guardianship, and even taught these arts to other humanoids.
Aurikesh backstory: The famed explorer Tharros of Valthandi was one of the first Sestomerans to set foot in the untamed wilds of Hullorne, where he found a tribe of veytikka who worked upon a sacred loom, weaving a cloth that protected like armor, by the blessing of Sioctana. Tharros attempted to bargain for the loom, but the veytikka rebuffed him, for this weaving was given to them by the Steadfast Goddess. Pretending to leave the village, Tharros waited until midnight and attempted to steal it. Just two veytikka tried to stop him - a sorcerer and a tempest-priest. The power that they called down against Tharros struck true and slew him, but infused the loom also. Sioctana's grace passed from the loom, to be replaced by Ychirra's blessing.
In the morning the veytikka came to understand what had happened, and they were filled with sorrow. Some of them went away to join other Baliothan clans; some continued weaving, and embraced the power of this new cloth, for guardianship or vengeance. In time they shared this magic with a select few humans and kagandi (and, in principle, might do the same with beruch). Two of the veytikka who joined Parthala were Stormcloaks.
At 3rd level when you adopt this archetype, when you hit a creature with a weapon attack, you can expend one ranger spell slot to deal lightning or thunder damage to the target, in addition to the weapon's damage. The extra damage is 2d6 for a 1st-level spell slot, plus 1d6 for each spell level higher than 1st, to a maximum of 5d6. The damage increases by 1d6 if the target is wearing predominantly-metal armor.
When you are grappled or swallowed whole, you can spend spell slots to deal the lightning or thunder damage specified above without making a weapon attack. The target may avoid this damage automatically by releasing you. (As usual, this does not require an action.)
The Power of the Cloak
Starting at 7th level, you gain resistance to lightning damage and resistance to thunder damage. Whenever you suffer damage of either type, you may spend your reaction to absorb some of its power into your weapons instead of grounding it out harmlessly. One weapon of your choice becomes empowered until the end of your next turn. The first time you deal damage with the empowered weapon, it deals an additional 2d6 points of lightning or thunder damage (whichever you absorbed). If you combine this effect with your Tempest's Lash feature, you instead deal 1d6 more damage than your expended spell slot would grant.
Furthermore, whenever you would suffer disadvantage on Perception checks due to heavy rain, snow, or sleet, you do not suffer disadvantage and instead gain advantage.
Starting at 11th level, the lightning and thunder that you command become all the more deadly when you strike twice. When you make two successful weapon attacks in a single turn, one target that you damaged in this round suffers an additional 3d6 thunder damage.
In the Storm I Rise
Starting at 15th level, when you use the Power of the Cloak feature, you also gain temporary hit points equal to the damage suffered or 10 hit points, whichever is less. These temporary hit points last up to 1 minute. While these temporary hit points remain, you can spend a bonus action to fly up to your speed. If you move during the round as part of your action, this move can also be flight. If you do not land on a surface that can support you at the end of your move, you fall. If you lose your temporary hit points in the midst of a move (perhaps from an opportunity attack), you fall.
My goals here are fairly clear: this is an intersection of paladin-style smiting (just as I used in the Lantern-Bearer, toned down by a die size so that the paladin isn't overshadowed in their Special Thing) and some of the powers of the Tempest cleric and Storm sorcerer. As with everything I write, I scrupulously avoid granting immunity to a damage type, but The Power of the Cloak and In the Storm I Rise are resistance-plus. Just as the Lantern-Bearer is the best person possible for the job of guiding people in darkness, the Stormcloak is the best person possible for the job of navigating in the midst of a storm. Were I to modify the class further, I would give them ways to reduce forced movement from wind, and maybe ways to guard allies from lightning and thunder damage. The main reason not to do that, as I see it, is that I don't want to create too much competition for the Stormcloak's action economy.
This is hardly the first time D&D has had a storm-themed ranger: the Stormwarden is a paragon path of the 4e Ranger. The Stormwarden only has one feature that deals lightning damage, though - its 16th-level damage aura. My Stormcloak is intended to be just as accessible and desirable for archer rangers as it is for any kind of melee ranger, where the Stormwarden was melee-only (an artifact of 4e ranger design).