Asp Lick

The touch of your shadow-wreathed hand can siphon life force from others to heal your wounds. Make a melee spell attack against a creature within 5ft. On a hit, the target takes 3d6 necrotic damage, and you gain hit points equal to half the amount of  damage dealt. 

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d8 for each slot level above 1st.