Storm Blade

You learned to strike suddenly like a distant clap of thunder, shield yourself with a whirlwind and cause lightning to strike at your foes.

It seems wherever you go dark clouds follow and a rolling thunder echoes in the distance. People feel uneasy around you but they never know why until it is too late. The cold steel of your longsword through their skin but when they thought they could outwit the damage you dealt, then they feel it; A surge of electricity pulsing through their veins. As quick as you drew the blade, your out of sight so long as the guards don't look up to the sky.

All you know is the storm guides you along your journey and you know it will reward you, so you ride it to your next destination.

Thunder Clap

3rd level Storm Blade feature

When you make a successful weapon attack roll with a weapon that doesn't have the heavy or a special property, you can expend a bonus action to apply lightning or thunder damage (your choice) to the damage roll. Roll your sneak attack dice and apply the total as the chosen damage type.

However, you cannot execute a sneak attack until the start of your next turn.

Wind Whisperer

3rd level Storm Blade feature

You gain the gust cantrip. You choose the spellcasting ability when you gain this feature; You can choose either Intelligence, Wisdom or Charisma as the spellcasting ability.

In addition, as part of the bonus action granted by cunning action you can cast this cantrip.

Charisma

You picked charisma for the spellcasting ability.

Intelligence

You picked Intelligence for the spellcasting ability.

Wisdom

You picked wisdom for the spellcasting ability.

Tempest Veil

9th level Storm Blade feature

Whenever you use your bonus action to commit either your Thunder Clap or Wind Whisperer feature, you gain the benefits of the warding wind spell until the start of your next turn.

In addition, you gain resistance to lightning and thunder damage.

Lightning Rider

13th level Storm Blade feature

Whenever you commit a cunning action, you gain a flying speed equal to your walking speed until the start of your next turn. 

Gathering Storm

17th level Storm Blade feature

After you deal damage to a creature with the Thunder Clap feature; At the start of the creatures next turn, you can force the creature to make a DC(8 + proficiency bonus + dexterity modifier) dexterity saving throw or take half your sneak attack dice (rounded up) in lightning or thunder damage (chosen when committing the Thunder Clap feature). The creature takes half the damage if they succeed on the saving throw.

You can do this a number of times equal to your proficiency bonus before a long rest.