+2 CON, +1 WIS

Use a bonus action to curl up into a ball. While in this state you cannot move yourself, however if moved by an outside force such as gust of wind, then you will roll around at a speed equal to the distance of which said attack, spell, etcetera would typically move you.  You move in the direction of which you were hit over the course of the following three turns; this includes all creatures turns.  If you are on a slippery surface such as ice or grease, then your rolling speed is doubled.  If contact is made with a surface or structure; such as a creature or wall, you bounce off that surface without taking a penalty to your speed; DM decides in which direction you begin to roll based on circumstances. Creatures that make physical contact with you must make a CON 12 DC, if failed they take 1D4 piercing damage.  In this state you are also resistant to piercing damage. To exit Spike Ball, use a reaction or bonus action to return to your normal stance.

At level 6 your Spike Ball now deals 1D6 Piercing damage, and 1D12 at level 12. Blades slide off of your back at level 15, making you immune to slashing damage as a Spike Ball, and resistant normally.

You have proficiency in the Endurance skill.