Aer, Greatsword of the Heavens

This magic greatsword is made entirely of a gleaming silver, inscribed with runes related to the Elemental Plane of Air. This blade feels almost weightless, and attacks made with Aer are often accompanied by a small gust of wind.

You gain a +3 bonus to attack and damage rolls made with this magic weapon. In addition, it has the following properties. 

Weightless. Aer only requires one hand to wield and has the finesse property. Due to the lack of mass, however, the sword often finds itself lacking force, dealing 1d6 slashing damage instead of the typical 2d6 for a greatsword.

Air Infused. Due to the spark of the Elemental Plane of Air infused within the blade, this weapon deals an extra 3d4 lightning or thunder damage on a hit (your choice).

Quickened Steps. Three times per long rest, you can invoke some of the runes inscribed on the blade. These runes create gusts of wind underneath your feet, granting a bonus to your current speed equal to 5 x half of your Dexterity modifier (rounded up), with a minimum bonus of 5 feet. This additional speed can be used to hover a maximum of 5 feet off of the ground, and lasts for 1 minute. 

Air Slash. Once per day, you can invoke the magic of the sword to compress and the launch a sharp blade of air at nearby foes. Make a ranged attack roll against all enemies within a 30ft. cone originating from you. On a miss, the creature feels a slight breeze pass by them. On a hit, the creature takes 8d6 bludgeoning damage and must make a DC 17 Strength (Athletics) check or be knocked prone. Flying creatures have disadvantage on this check.

Proficiency with a Shortsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: creature of non-lawful alignment, Finesse, Light, Vex