No one remembers who the first Arcstrider was. Hardly anyone remembers the Arcstrider at all. Time vanished us like it does memories.
But in the darkest days of the Dark Ages, when humanity was utterly defenceless, Arcstriders disciplined their bodies to let the Traveler's energy flow through them, to call lightning itself to hand and wield it like a staff against the Darkness.
Become the Lightning, they said.
No.
Become the staff, they said.
No.
Become a weapon, they said.
We obliged.

Arc Form

• Your weapon attacks deal an additional 1d6 lightning damage
• Creatures you have grappled take 1d6 lightning at the start of their turn
• Wearing armor does not impose disadvantage on Stealth (Dexterity) checks
• Your movement speed increases by 5 feet
• You have resistance to lightning damage and thunder damage

You can use this feature twice and regain all expended uses at the end of a long rest.

Retaliation Arc

Also at 3rd level, when a creature hits you with a weapon attack, you can use your reaction to cause of arc of thunder to hit the creature. The creature must make a Strength saving throw. On a failure, the creature takes 2d6 thunder damage and the creature is pushed back 10 feet. 

You can use this feature a number of times equal to your Constitution modifier (a minimum of once). You regain all expended uses when you finish a short or long rest.

Arc Staff

Wield lightning as a weapon.

Striders March

At 5th level, you’ve learned the art of assaulting the enemy from all fronts. You gain proficiency in  (Stealth) checks and may add double your proficiency, your walking speed increases by 10 feet, and you may use the Dash action as a bonus action on your turn.

Additionally, you have an advantage on  (Stealth) checks made to hide in a storm.

Stunning Jolt

At 7th level, you’re able to harness the static electricity in thin air in attempts to shock an enemy, shutting down their primary systems temporarily. When you hit a creature with a melee weapon attack, you can force the creature to roll a Constitution Saving Throw against your Arc Strider DC (8+Prof+Con Mod). On a failure, the creature is stunned until the end of its next turn. 

You can use this feature a number of times equal to your Constitution modifier (a minimum of once). You regain all expended uses when you finish a long rest.

Thunderous Leap.

Move like a Strike of Lightning, Shifting to a location you can see within 60ft without expending Walking speed. Creatures within 10ft of the landing location must make an agility (Dex) saving throw, on a failed save receiving 2d12 Lightning damage or half as much on a successful save. This may be used Twice per Long rest or As a bonus action without using its usual charges while in Arc form.

Cyclone Surge

At 13th level, you can combine the element of wind and lightning to your advantage on the battlefield and the like.

As an action, you may transform into a cyclone of pure electrical energy. You are classified as large while in this cyclone form, which lasts until the beginning of your next turn. When a creature starts its turn within 60 feet of the cyclone, you can force the creature to roll a Strength Saving Throw against your Arc Strider DC and take 2d10 lightning damage, half as much on a success. On failure, the target is also pulled 15 feet towards you. Creatures that are pulled into the cyclone take an additional 6d10 Lightning damage and are blinded and deafened. You regain the use of this feature at the end of a short or long rest.

Part of a Storm

• Weapon attacks against creatures made of or wearing metal are made at advantage.
• Your weapon attacks deal an additional 1d12 lightning damage on hit
• Grappled creatures take 2d12 lightning damage at the start of their turn
• Wearing armour does not improve the disadvantage on Dexterity (Stealth) checks
• Your movement speed increases by 20
• As an action, you can force a single creature within 60 feet of you that you can see to make a Dexterity Saving Throw against your Arc Strider DC or become grappled and restrained. A creature can use its action on subsequent turns to attempt to escape this grapple.
• You can change your physical form to become pure electrical energy. You can choose this form when you enter your Arc Form or as a bonus action on subsequent turns, you can also exit this format will (No action required). While in this form your weapon attacks deal lightning damage.  Everything you’re carrying that isn’t your equipped weapon and armour is temporarily merged into your new form. While in this form, you can move through cracks as thin as 1 inch wide. Additionally, you can end your turn in another creature’s space. When you do so, you take 1d12 force damage while the creature takes 1d12 lightning damage.
• You have immunity to lightning damage
• You have resistance to thunder damage

You can use this feature twice and regain all expended uses at the end of a long rest.