Arcane Duelist

You have trained in the art of weaving spells in your off-hand as deftly as two-weapon fighters strike with parity.

When you take the Attack action on your turn with a Light weapon you wield in one hand, you may also make an off-hand melee spell attack as a bonus action.  This attack uses your Spell Attack bonus and deals 1d8 damage of one of the following types: acid, cold, fire, force, lightning, necrotic, poison, psychic, radiant, and thunder. 

This damage increases by 1d8 each at Caster level 5, 11, and 17.