Kinetic Battery

You've learned how to magically store up the forces created with your attacks.

You gain a +1 bonus to one ability score of your choice, up to a maximum of 20.

As a Bonus Action you can activate Kinetic Battery, which lasts until you deactivate it as a Bonus Action. Each time you hit a creature with an attack, you store a number of points of damage equal to half your proficiency bonus (rounded up), storing up to a maximum of your level + your ability modifier associated with your attacks; this stored damage lasts for one minute, after which it decays. On a following turn within one minute, you can deactivate this ability using a Bonus Action to cause your next successful attack to deal additional damage equal to the amount you stored; if you don't attack within this minute, the damage bonus decays. When you've dealt damage this way, the next time you take damage within the next minute, you reduce it by and amount equal to the damage you stored with Kinetic Battery.