Source: Player's Handbook
Prerequisite: Level 19+
You gain the following benefits.
Ability Score Increase. Increase one ability score of your choice by 1, to a maximum of 30.
Last Stand. When you would be reduced to 0 Hit Points, you can drop to 1 Hit Point instead and regain a number of Hit Points equal to half your Hit Point maximum. Once you use this benefit, you can't use it again until you finish a Long Rest.
Recover Vitality. You have a pool of ten d10s. As a Bonus Action, you can expend dice from the pool, roll those dice, and regain a number of Hit Points equal to the roll’s total. You regain all the expended dice when you finish a Long Rest.