Lost Leaves Fallen Shadow technique

You have learned an ancient sword technique. You gain the following benefits:

• When you take the Attack action and attack with a sword with both hands, you can swing the blade in an arc around you attempting to hit any enemy in reach. Roll once to hit and compare AC to every enemy in reach to determine if they are hit.
• This technique can only be used as many times as your proficiency bonus before requiring a short or long rest