Hero's Focus

You're not just any random adventurers, you're heros of legend!(Even if you don't know it yet)

As a hero, you have the uncanny ability to focus your energy into whatever you do, letting you perform feats nobody but you can!

You gain 2  focus points. Requiring no action, you may spend one focus point to increase(or decrease) the dice roll of an attack roll, ability check, or saving throw you make by one(multiple focus may be spent on a single roll). As well, you can spend focus points when an enemy makes an attack roll against you, makes a saving throw against an effect you create, or makes an ability check in contest with you. This can be done after the roll is made, but before any of the effects take place, and may potentially negate a critical fail or create a critical success(or vice versa). All focus points are reset back to 2 the end of a long rest, and any unspent focus points disappear. Additionally requiring no action, you may roll any number of hit dice and take damage equal to the total rolled. If you do so, you expend those hit dice, and you gain a number of focus points equal to the amount of hit dice rolled.