Bloodcrazed

When you are grievously injured, you can enter a bloodthirsty frenzy to attempt to restore some of your health.

At the start of your turn, if you have taken damage since the end of your previous turn, you can enter a frenzy (no action required), which lasts until the end of your current turn. Whenever you hit a melee attack during this frenzy, you regain a number of hit points equal to your proficiency bonus. You cannot heal to higher than half your maximum hit points using this feature. You can enter this frenzy a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.