This warhammer sparks and sizzles quietly in the hand of someone who attunes to it.  You have a +1 bonus to attack and damage rolls made with this magic weapon.

Voltaic Soul. When you land the final blow against a player or monster with this weapon, a bolt of lightning reaches out to the nearest creature, up to 30 feet (including whomever wields this weapon, at DM's discretion).  That creature makes a DC 13 Constitution saving throw, taking 2d8 lightning damage on failure, or half as much on save.   

If the creature taking lighting damage fails the save, repeat this process again until a creature makes the save.  This chain can effect up to five creatures in this way if there is no successful save. 

Proficiency with a Warhammer allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Magic, Damage, Combat, Versatile, Push