Tony Monk's License to Shred

Your bloodline from eons past and future imbue you with the knowledge of how to shred in ways your enemies would assume are impossible.

When you hit a Large or smaller creature with your Unarmed Strike, after you deal damage, you may spend a bonus action to use 3 Focus, and must say "kickflip this, numb-nuts".
Upon doing so, the target must succeed on a Constitution saving throw (equal to 8 + Dexterity modifier + your Proficiency bonus), or be transformed into a 8.5in wide, 32in long skateboard, with a deck scrawled with graffiti that spells "NAT 20", and hot pink wheels, until the end of your next turn.

When the creature is a skateboard, they are Blinded, Deafened, and Incapacitated.
The skateboard has 3d6 hit points, an Armor Class of 13, and Immunity to nonmagical Slashing damage. If the skateboards hit points are reduced to 0, the transformation ends early. if the transformation ends in this way, any damage exceeding the skateboards remaining hit points is dealt to the target when the transformation ends.
Until the transformation ends, you may substitute one of your attack rolls to begin a "trick sequence" on the skateboard. Each trick must be announced before you do it, you cannot repeat the same trick during the sequence, and the sequence can only go up to 6 tricks. Upon doing the first trick trick you must make a Athletics check with a DC of 6, and must make another adding +3 to the DC for every subsequent trick. This ends once you fail a check, or succeed on the 6th trick.
Once the trick sequence has ended, you hop off the board and the target's transformation ends, and they take 1d8 Psychic damage for every successful trick in the trick sequence.

If the target's transformation ends inside an enclosed space that their normal form cannot occupy, they take 4d4 force damage and are moved to the nearest unoccupied space.

You may use this ability a number of times equal to your Proficiency Bonus per long rest.