Devouring Touch

You reach out with a force of insatiable hunger, taking from others that which you need to live. As an action, you make a melee spell attack against a creature you can touch. On a hit, the target takes 1d6 necrotic damage. You then regain hit points equal to half of the damage dealt, rounded up. 

This spell has advantage against creatures whose size category is larger than the caster's.

This spells damage increases by 1d6 when you reach 5th level (2d6), 11th level (3d6), and 17th level (4d6).