Source: Unearthed Arcana 85 - Wonders of the Multiverse

Prerequisite: 4th Level, Scion of the Outer Planes (Evil Outer Plane) Feat

You can channel cosmic forces of evil that cause pain but invigorate your being. You can choose your own actions despite this malign connection. You gain the following benefits:

• Ability Score Increase. Increase an ability score of your choice by 1, to a maximum of 20.
• Life-Draining Grasp. Once per turn, when you hit a creature with a melee weapon attack, you can also deal necrotic damage to it. The damage equals 1d6 + your proficiency bonus, and you regain a number of hit points equal to this necrotic damage dealt. 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.