You gain the following benefits.
When you roll a Hit Point Die to regain Hit Points, you can treat any roll of 1 or 2 as a 3.
Once per turn when you hit a Bloodied creature that isn't a Construct or Undead with an attack roll, you can expend a Hit Point Die, roll it, and regain a number of Hit Points equal to the number rolled plus your Constitution modifier.
You can use this feature a number of times equal to your Proficiency Bonus, and you regain all expended uses when you finish a Long Rest.