Prerequisites: the Vampire feat

Your fangs have sharpened and your bloodlust has grown. It now only takes 24 hours without drinking blood to suffer the effects of starvation. In turn, you gain the following benefits:

• Increase your Constitution score by 1, up to a maximum of 20.
• Once per turn when you use your fangs to make an unarmed strike against a creature, you can expend one hit die and regain a number of hit points equal to the number rolled. You can use this feature a number of times equal to your constitution bonus (minimum of 1), after which you must complete a long rest before using it again.